Autoweek figures that the “dramatic decline in diesel fuel price” is what’s causing VW and Mercedes diesel sales to increase as a percentage of total sales in recent months. But only VW’s Jetta, and M-B’s ML, GL and R Classes have diesel options to take advantage of the mini-boom. To be fair, though, not many would have predicted a year ago that Jetta diesel sales would approach 4k units per month (3,862 in May). But will it last?
According to etrucker.com, diesel prices have risen for seven straight weeks for a total increase of 43.1 cents per gallon (national average). Of course, the national average for gasoline is also up .67 cents in the last 50 days. On the other hand, a look at the good old government price tracker shows that California’s averages display the greatest price discrepancies with gas at about $3 and diesel at $2.79.
Any guesses as to the percentage of these pricy diesels being bought in the Golden State? Based on an uptick in street sightings here in Portland, OR, not all the new Jetta TDIs are moving to Cali. But if the economy (specifically real estate) is ever going to recover, isn’t this boomlet bound to bust?
Maybe Honda will bring its US diesel program back out into the light. Honda needs to do something. The New Insight is fizzling already. Toyota has pulled further ahead of the pack with the 2010 Prius, and the Ford Fusion Hybrid is an excellent entry as well.
Honda is in grave danger of becoming an also-ran akin to Nissan.
I do think there is more pent up demand for diesel engines in this country than the auto companies believe.
Every diesel motor that you can buy in the US right now seems to be awesome. I never cared much about diesels, but after reading tons of glowing powertrain reviews about the E320, 335d, Jetta TDI, Chrysler 300 CRD, Duramax V8, and Cummins I6- I’ve definitely gained in interest in them.
The price premium charged for diesel cars may begin to drop as fuel economy standards force gas engines to adopt things like spark ignition, direct injection, and turbo-charging to make their power.
The Jetta TDI Sedan and SE Sedan are options-comparable, with the TDI approximately $2200 more expensive (MSRP). The TDI gets 9/11 better mpg according to the EPA.
So assuming you get the city mileage in both cars (to be conservative) and both gas and diesel are $3 per gallon, you’ll recoup the additional cost at approximately 50,000 miles, after which you’re saving money. This doesn’t take into account any other benefits/disadvantages of the platforms, such as longevity, resale or performance.
If diesel goes up to $5 and gas stays at $3, you’ll lose an additional $1200 (approximately) over that same 50,000 miles. That’s somewhat less than $250 every 10,000 miles.
So whether it makes financial sense depends on (a) your patience, (b) relative fuel prices, and (c) whether you think there are other tangible benefits (perhaps you believe diesels are more reliable, or have better resale value, or that gas-powered cars are more fun to drive, or have better resale value) but they’re valid choices, certainly.
Not to worry. VW reliability will fix the desire for Jetta diesels. Direct ICE injection is being introduced now. Computer controlled solenoid valving next. Maybe HCCI will work out also.
The $1300 US federal tax rebate on Jetta TDIs probably isn’t hurting sales either. With the C4C program, the gov’t will kick in a total of $5800 towards you new TDI, assuming you have a suitable vehicle to scrap.
http://www.hybridcars.com/federal-incentives.html
Honda is in grave danger of becoming an also-ran akin to Nissan.
They still make solid cars, which is pretty important in the grand scheme of things.
They can just refresh their fleet with their crummyish hybrid tech to abide the new CAFE and come out ok.
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The Jetta TDI Sedan and SE Sedan are options-comparable
Diesels have the low-down torque, but lack power. You basically get maybe 5-10% improvement once you factor in the 20% greater density and similar power/technologies.
“Not to worry. VW reliability will fix the desire for Jetta diesels.” Is VW reliability that bad? Those Jetta deisels sound good. I have friends around, and at work with regular gas Jettas, and never hear thme complaining. Just wondering about what you know that I haven’t heard…
Has Volkswagen ever been able to shake lose those electrical gremlins that plague their entire line? I purchased a 2000 Passat GLX New that developed phantom electrics after 19,000 miles and dumped the car around 23,000 miles. Good move, as Consumers trashed the car in years to come. I love diesels, but have no faith in European electrical systems.
I really would love my next car to be a diesel. But the availability in my area is nonexistent. I’m hoping V-dub will set up shop in a locally shit-canned Chevy dealership, but since I live in UAW central I doubt that’ll ever happen. I’ll probably just have to set my sights on a regular four-banger, hopefully with DI.
Will it be super $$$ to repair?
I think a lot of the appeal of diesels is just having something different. For some people (myself included) the huge popularity of the Prius, Camry, Accord, Corrola and Civic are big negatives in terms of wanting to own one. Who wants to have the same thing that everyone else has?
I’m not sure that the boomlet will bust.
I’ve never owned a diesel, but a 4-cylinder car that has a million pound-feet of torque at 1500 rpm and can tow my camper while getting 40 mpg makes just about everything else look silly, regardless of gas prices or the economy.
Just find me one that isn’t made by Brokenwagen, and I’ll be the first in line.
Ay-freaking-men, Bocatrip. I would buy a Volkswagen diesel before lunch tomorrow if I had any faith in European electrical systems.
I’ve yet to meet anyone with a Volkswagen of any vintage that didn’t suffer some bizarre, eye-rolling electrical problems more than once, and I’ve got better things to do with my life than chase down electrical gremlins that start five seconds after the warranty expires. Like, for example, I’d rather watch reality TV while chewing on tinfoil.
davejay:The Jetta TDI Sedan and SE Sedan are options-comparable, with the TDI approximately $2200 more expensive (MSRP).
I was in the checkout line at Autozone and saw a copy of the NADA Orange Book, so I briefly looked up my TDI…and found, IIRC, my 2003 had a $2000 premium over the gasser….so that premium isn’t a just a bullet in the head any more that any other option you might tack on.
Not that any of us are looking to trade in…we all drive our cars pass the point of resale, so that’s a bit moot. OTOH, if you hit a deer, that extra $2k in value may make the difference between getting your car totalled by the insurance estimator or getting it fixed….and if you’re like me, you’ve done various driving mods (Bilsteins, SRS suspension, special this and that) that fit you like a glove but don’t add a cent to the valuation….and you’d rather have the car fixed than get it totalled and a check for 2-4 months of payments on a car loan.
But only VW’s Jetta, and M-B’s ML, GL and R Classes have diesel options to take advantage of the mini-boom.
And what happened to VW’s Tourag TDi and BMW’s 335d and X5 3.5d (hate that new stupid xDrive and sDrive BS)?!
I wonder how many takers are for BMW diesels? So far, I’ve seen only one X5 3.5d in Toronto area, but plenty of G-Class and some ML-Class Mercs. Also quite a few of Jetta TDi.
I’ve got a 5-speed 2004 Jetta TDI (1.9 Pumpe Duse) wagon that I bought new in October 2003. It’s been a great car. It’s approaching 60,000 miles and it’s never stranded me. The total problems I’ve had with it are:
1) Minor (dripping) fuel leak at a camshaft-mounted pump. Repaired under warranty.
2) Recall for seat heaters.
3) Leak at water separator. Repaired under warranty.
4) Left front marker light sometimes goes out after the car sits overnight after a heavy rain. I think there’s a small leak somewhere by the bulb, but I haven’t bothered to investigate it yet (the bulb works after it drys out).
5) A coolant temperature sensor began acting up after the warranty expired. An easy $16, 5 minute fix.
That’s it.
I’m getting 49 mpg average and around 650 miles per tank commuting to work. I drive gently, but run 60 mph on the highway, so I’m not hypermiling by any means. I’ve never gotten less than 42 mpg.
I think most of VW’s reputation for electrical problems relate to bad ignition coils in some of the 1.8T gas engines, but those were resolved long ago. The TDI doesn’t have coils. ;-)
Every manufacturer can have lemons. Don’t be afraid of recent TDIs from VW, IMHO. They’re great cars.
Cheers,
Scott.
One VW dealership I passed recently…every jetta wagon on the lot was a TDI. Maybe they think they’re onto something.
I drove a 335d recently and I was extremely impressed by everything about it. It’s no more expensive than an identically equipped 335i (costs about the same as a 335i auto) and slightly cheaper once the rebate is factored in. The fuel economy is lacking for a diesel (22/36, I believe) but the torque is addictive and the 500 mile cruising range is appealing.
I have a 2002 Passat GLX 4motion with no electrical problems, except had to re-seat the fuse for the radio twice.
I had a 1995 Maxima whose engine computer completely died on a ramp in a parking garage. Nice. The whole electrical system went stone cold dead.
That being said, the Passat has had a CEL for the past 30K; replacing all FOUR cats will cost more than $2.2K before next inspection.
So, in spirit, the advice abut VW is still worthwhile.
When I trade cars with my wife for a day, I experience the diesel difference in reverse. Her Subaru Forester is quiet at idle but somewhat noisy at speed. My Beetle TDI is just the reverse. The faster you go, the quieter the engine gets.
Although the Forester has a big, torquey engine for its class, it’s always making me downshift to hold velocity on hills and to accelerate away from intersections. Whereas the turbodiesel seems not to notice hills. I can pull away smoothly from low-speed street intersections in third gear, whenever I want. If the TDI had only two gears, second and fourth, it would still work quite well.
If Americans really hate to shift gears manually, as they do, they ought to know this advantage of turbodiesels- shifting is optional in most situations. Add in the much improved mileage, the ready access to boosted torque at any elevation, and the impressive resale value advantage, and I can’t see myself every buying a gas-burning car again.
BTW, either the headline of this story needs correction. or I didn’t get the joke. “Aa” is a Hawaiian lava, isn’t it?
I own a 2003 Honda Element and my wife has owned three Hondas since 1988. They are very solid cars and very uninspiring vehicles. Some people like those kind of cars. I do not.
I would love to sell my Element and pick up a diesel Golf. If the VW dealer in Poughkeepsie had not been such an ass, then I would have diesel Jetta wagon instead of the Element.
One of my coworkers drives a gas powered Golf and loves it. No problems through the first two years of ownership.
I’ve lost interest in VW ever since they began those idiotic Apple-esque ads of late (stupid talking Bug). I don’t want to buy a car because of the hipster-doofus appeal; I want a car that is reliable. In Europe, VW does not try so hard to be assbackwards “quirky” in it’s presentation. But here in the States, well…lets appeal to the tight black jeans and aloof 20/30-something crowd. Um, no thanks.
BTW: The latest ad for the TDI Jetta makes the claim of 47mpg (“Guiness World Record”), but the damn font size of the legalise at the bottom is smaller than you see on a Billy Mays infomercial. Sure would like to see what the hell the “if/ands/or buts” are. Thanks VW, I’ll skip you again this car buying trip. Come back when you want to sell to adults…
@Sammy Hagar :
In Europe, VW does not try so hard to be assbackwards “quirky” in it’s presentation.
In Europe, VW is a mainstream brand. Boring. Good resale value. Cheap to fix. The safe choice. Deales don’t charge insane amounts for maintenance like the Japanese brands do.
Weird how it’s completely different in the US. I still can’t get my head around the fact that Americans under the age of 70 seem to like Jettas,
lutonmoore:
Just wondering about what you know that I haven’t heard…
He (RogerB34) doesn’t know – he’s just throwing things out there just to be annoying.
I’ve owned and worked on VWs for almost 30 years. I can tell when somebody knows what they’re talking about in regards to this brand, and who is basically talking out of the other end…
A well-maintained VW will last for years…
Sammy Hagar:
I’ve lost interest in VW ever since they began those idiotic Apple-esque ads of late (stupid talking Bug).
I’m sure there are plenty of other automotive appliances out there that will suit your needs…
truenorth:
That being said, the Passat has had a CEL for the past 30K; replacing all FOUR cats will cost more than $2.2K before next inspection.
If you take it to a VW dealer, it will.
If, on the other hand, you can locate a private VW mechanic or a VW tuner, it will save you some serious $$$$ for the exact same job.
I’ve yet to meet anyone with a Volkswagen of any vintage that didn’t suffer some bizarre, eye-rolling electrical problems more than once
Word. My friends Passat wagon is veritable Hallowe’en horror show of electrical gremlins. He’s hoping for the day that he can actually get everything working concurrently so that he trade it in. VWs suck.
I have a 2002 Passat GLX 4motion with no electrical problems…. I had a 1995 Maxima whose engine computer completely died.
Comparing a 26 year old mistress to a 90 year old grandmother is not exactly fair. Is this what it takes to make VW look good?
Interesting. My 95 Golf has never had an electrical problem ever in 229,000 miles. Its had other issues, but never an electrical problem.
Yes, you should have a good VW mechanic. But you should have a competant mechanic who you can trust no matter what kind of car you have.
I am interested in the diesel golf, i hear they get liks 50 mpg. I approve.
However, they can be pricey, and the Golf is already pricey in its segment. At some point, it just isn’t worth it.
I was hoping to get one, assuming that VW imports them AND had the C4C program not punish those who did the right thing years ago with a fuel efficient car.
My golf gets 29 mpg officially, the diesel VW’s all get better than 10 mpg more mileage. Which would have made me eligable for the $4500 rebate.
For which I am not eligable.
Three VW’s ’98 Passat, ’04 Passat and a ’08 GTI none ever had an electrical problem.
For eco-weenies who are not obsessed with cars, the Jetta TDI and the Toyota Prius seem comparable. The fuel economy is the number that catches their interest, and it’s the only number they understand.
On the inside, the Jetta seems roomy, and the car seems less “cheap.”
At least that’s what I’ve heard from the few Jetta diesel owners I know.
Why must every discussion involving VW products devolve into rants about reliability? I read this topic to be “diesel or not,” and framed my reply accordingly. Maybe a Mercedes diesel car would be more reliable; I doubt it would be easier to fix. Modern VW’s are packed with as many electrical conveniences as luxury cars, but built to sell at a lower price. Their US buyers typically aren’t rich enough to laugh off the service costs, as BMW or Mercedes owners might.
My ’02 NB TDI would have been cheaper to maintain if it hadn’t come with central locking, cruise control and a sunroof. All have needed repair. But none of these flaws left me stranded beside the road. There have been inconveniences, but hey, it’s a 130,000-mile used car. Which was not the subject of this discussion.
What will the long-term trend be for diesel prices be? Csere Csaba wrote this column last year:
http://tinyurl.com/4ektm7
I haven’t seen a better take on price/demand/supply for diesel, and if this is correct owning a diesel will not be a good long-term investment. Would be interested in hearing others’ perspective on it.
Also, when figuring $/mile on diesel engines, if the car is a mercedes does anyone figure in the cost of the urea refills?
The injection pump went recently on my 2003 Jetta TDI. I don’t blame VW for that though. It’s either something Bosch did wrong (they made the pump), or it’s my fault because I didn’t regularly add any diesel additives in the tank. Since ULSD came in 2007, it might be responsible for doing it. But either way, it cost me $1000 to fix and wasn’t fun. The engine itself has been great and problem free. No oil usage, and I typically get about 35-40 MPG combined. I used to get 52 MPG regularly when I did a lot of highway driving.
I’ll likely replace my car in a few years with a Golf TDI because I really want a hatchback. KBB says my car is worth $8600 right now for a private party sale, and I don’t owe a cent on it.
The same car with a gas engine is worth less. So I don’t even consider the “diesel premium” as a valid argument. You can either spend a couple thousand extra on a decent engine, or you can buy a navigation system that isn’t actually worth $2000 when you can get a TomTom or something similar for $200 or less.
I personally believe that VW would do well in the US to extend more bare bones offerings like the Rabbit.
The germans aren’t particularly keen to following the engineering mantra “K-I-S-S” but they would alleviate many of the perceptions that americans have of VW unreliability if they did, in fact, create a very simple and dependable vehicle.
They have the position, ability, and desire to take a strong market share in the US…a home run similar to the original Bug may do real well here.
The first generation of Saturn did it well, but screwed it up…VW has a second chance.
Let’s see some more dispatches from the religious war between proponents of diesel vs hybrids as to which fuel-saving technology is really more economical and better for the environment.
This topic sort of amuses me, in that the most passionate of diesel advocates seem to understand very little about what it is that they support.
Much of the fuel economy benefit on an MPG basis for diesel is due to the fact that diesel has more oil in it. If a refinery were to change its crack spread to increase diesel production, it would lose a correspondingly higher amount of gasoline production, because of the difference in the energy content.
In other words, if the spread is changed to produce one additional gallon/liter/etc. of diesel, you’re going to lose more than one gallon/liter/whatever of gasoline. The tradeoff is not even.
Look at it from the standpoint of how the entire barrel of oil is consumed, and the pro-diesel fuel economy argument falls apart. A barrel of oil refined more toward diesel will produce fewer gallons of fuel overall. The individual vehicles may have higher MPG’s, but because there are fewer G’s in the equation, you don’t end up with more M’s overall.
Diesel does have the advantage of operating with higher compression, but that benefit is being reduced over time as gas engine management systems improve. Diesels also improve their position with turbos, but those can be easily added to gas engines as well.
At the end of the day, there is no diesel advantage, unless you just personally like to drive them. We already consume a lot of diesel in industrial applications. If we were to radically change our usage, refiners would have to invest billions to adjust their crack spreads, which would make the cost of gas and diesel both increase as they attempt to recover their investments.
In any case, the diesel consumer is just exposing himself to the business cycle, because an economic recovery will increase demand for diesel, not just in the US but worldwide. That should lead to diesel prices increasing more quickly than gas prices when the economy improves. Not really a win here, folks.
@xyzzy :
Also, when figuring $/mile on diesel engines, if the car is a mercedes does anyone figure in the cost of the urea refills?
Is that a serious question? A gallon of AdBlue is around € 1.60 at any gas station in Europe. A GL-Class has a 8.5-gallon tank that is supposed to last at least 15,000 miles.
-> It doesn’t matter financially. At all.
Pch101: At the end of the day, there is no diesel advantage.
Them’s fightin’ words! Diesel is/has:
#1 Inherently more efficient, but he acknowledged that….then sortakinda said it didn’t matter.
#2 More torque at lower RPMs, which isn’t just only just fun (steaming up the hills while everyone else is rowing away with their gassers’ gearboxes) but allows you to more efficiently shift sooner and cruise at lower RPMs. I’m in top gear at 25MPH on the flat, mooching along at 60-70MPG.
#3 Real alternate bio-fueling….as opposed to rot your fuel system, low MPG ethanol. Tho both need improvment in waste-derived non-food competing feed stocks, biodiesel is further along on all fronts.
#4 When the next oil embargo/shortage hits and fuel is rationed, it’s the same as #2 Fuel.
I know I got 25-28MPG at best with my ’98 GTI VR6 Golf…even when I was doing a lot of conservative highway driving. My 2003 TDI gets
over 50MPG and would do even better….if I didn’t do highway driving where the air resistance of higher speeds kills the MPG.
So I get 15 to 25 MPG better than a gasser. Not much of a win, I guess……….Pch101 puts up a high bar :)
@ Mirko Reinhardt :
It was a serious question because I really did not know what Adblue costs.
I know I got 25-28MPG at best with my ‘98 GTI VR6 Golf…even when I was doing a lot of conservative highway driving. My 2003 TDI gets
over 50MPG and would do even better
Argh. So you want to compare a 90 hp diesel to a large six-cylinder performance motor based upon its fuel economy, while ignoring the enormous performance differences. To call that an apples-and-oranges comparison would be an insult to fruit.
You should know that what you’ve just done makes absolutely no sense whatsoever. A Honda Fit gets better fuel economy than does a Bugatti Veyron, too, but that has far more to do with the performance characteristics of a high-output engine than it does with the type of fuel that they use.
Inherently more efficient
A vehicle that is required to use a fuel that contains more oil is not inherently more efficient. The end result is that a barrel of oil can’t produce a given quantity of diesel without sacrificing a greater quantity of gasoline. The MPG fixation reveals an ignorance of basic chemistry.
#1 Inherently more efficient, but he acknowledged that….then sortakinda said it didn’t matter.
As I’ve mentioned above, that benefit is in the realm of 5-10%. That’s my simplistic calc comparing like to like engines, and if anyone has a better technical explanation based on the actual cycles, I’m sure we’d all love it.
–
biodiesel is further along on all fronts.
Yet it’s still somewhat of a dead end. Interestingly, I’ve heard of proposals to use intermediate forms of biological products to bypass any further processing into current forms of fuel. However that suffers the tremendous downside of not being interchangeable.
Pch101: At the end of the day, there is no diesel advantage.
Hmm. My 1984 Volvo Diesel station wagon (engine by VW, btw) has several advantages.
Most importantly, fuel is free, provided by my local Chinese eatery. None of those fancy heaters or dual-tank systems for me, I live in a desert.
I haven’t paid for fuel in the last 10,000 miles. Top that, Prius!
Most importantly, fuel is free, provided by my local Chinese eatery.
If your cousin owned a gas station and gave you free unleaded for a lifetime, would that make gasoline a superior fuel for the society as a whole?
There isn’t enough waste oil or arable land to meet more than a few percent of our current diesel needs, let alone what we would need if consumption increased.
Diesel is an oil byproduct. Gasoline is an oil byproduct. If we cared about resource efficiency, we would have a mix of vehicles that optimized the crack spreads of our refinery system, and use vehicles of both types that are as efficient as possible for their classes.
These my-slowpoke-diesel-gets-better-mileage-than-my-muscle-car-gasser and my-neighborhood-restaurant-owner-like-me comments are just not sensible, logical arguments. Compare apples to apples, and try to understand that there isn’t enough cooking oil to go around.
There are multiple different points being argued here and the honest truth is that it all depends on the part of the argument you agree too. Yes, it costs more in product and time to produce diesel fuel. Thus a mass market shift to Diesel would likely cause an overall increase in fuel prices.
However, I do believe (and correct this if I am wrong) that diesel would still be a better bet if overall prices increase because it is still more efficient (again assuming that the price difference between gas and diesel does not increase). Additionally, I assume that diesels are more adaptable to turbos due to their lower rpm band. However, much like hybrids, the cost of parts and labor are more scarce due to the relative obscurity of this technology in passenger vehicles. This likely tranlates to higher rates at the mechanic/dealership as well as an increased purchase price. If increased popularity lowers purchase price and cost to maintain, it will also lead to corresponding increases in fuel cost. So, it seems as if the only definitive answer in all this is to pick your poison and hope that it was correct. It does appear that A little DIY and willingness to go against the grain of popularity may lead to the most economical outsome at the expense of convenience.
A question for the B&B then, why are we not collecting all of the waste vegetable oil in this country and purifying it into biodiesel to subsidize overall fuel prices? Why does the country leave it to eggsalad and others to use it for free?
As Sanman111 said, there are several arguments going on simultaneously here. I don’t want to argue chemistry with Pch101 but I do think he overstates his case.
Yes, gasoline engine technology is improving, but there are fundamental limits that spark ignition engines have that limit their efficiency compared to diesels. In general, higher compression ratios give better efficiency in IC engines. My TDI has a compression ratio of 19, plus a turbo which effectively increases it even more. 11 is high for a gas engine, and 10 is high for a turbo gas engine like the VW TSI. Combustion efficiency is all about making sure that every possible carbon atom in the fuel is oxidized. Diesels excel at that because they’re a compression-ignition, not spark-ignition, engine.
In my case, I came to my TDI from a 1987 LeSabre with a 157 HP 3.8 litre V6. It got 20 mpg commuting, 30 mpg on trips. I wanted a small wagon with a manual transmission, reasonably large cargo capacity, and at least 4 seats, that got substantially better mileage because I knew that gas prices were going to increase substantially over the life of the car. My choices were extremely limited – only the TDI gave substantially better mileage in a wagon platform.
As we all know, when we talk about mileage we mean miles per gallon of fuel. Not miles per calorie. ;-) And we can only buy what’s available on the market. Academic arguments about crude cracking, or hypothetical super-efficient gas engines, and so forth are a distraction.
In the real world, TDIs get better mileage than gasoline cars.
Cheers,
Scott.
In the real world, TDIs get better mileage than gasoline cars.
In the real world, this is not true when you look at the barrel of oil from which the fuel comes. As noted, increased diesel production comes at the expense of a greater loss of gasoline production.
Arguing that MPG is some be-all, end-all argument is like claiming that chocolate cake is “better” than salad, because the cake contains more energy per ounce. That isn’t a logical point to make, and does nothing to deal with the big picture.
If refining an additional five gallons of diesel for you results in the loss of six gallons of gasoline for the rest of us, then we have solved nothing. More diesel results in fewer G’s to burn; you have to ignore some basic facts to believe that the “real world” is as you believe it to be.
A question for the B&B then, why are we not collecting all of the waste vegetable oil in this country and purifying it into biodiesel to subsidize overall fuel prices? Why does the country leave it to eggsalad and others to use it for free?
It’s already being recycled, at a cost to the restaurant. They’re just taking advantage of that system. Eggsalad’s processing also probably results in a very polluting car, even greater than the usual carcinogenic nature of diesel exhaust.
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In the real world, TDIs get better mileage than gasoline cars.
You didn’t refute any of claims above regarding efficiency, and in fact only repeated the fallacies. At least take a look at the BSFC or even epa numbers for similar cost/power engines.
Pch101 writes:
In the real world, this is not true when you look at the barrel of oil from which the fuel comes. As noted, increased diesel production comes at the expense of a greater loss of gasoline production.
You’re repeating yourself. Again, look up the definition of mileage. ;-)
FYI, it’s not a hard-and-fast rule that diesel comes at the expense of gasoline, especially as the light sweet crude gets more dear. In fact, one can make the case that gasoline is coming at the expense of diesel The Oil Drum:
The amount of gasoline originally in the crude varies from well to well. In the example I posted the blue line shows that there is about 14% (eyeballing the curve) of the original that will be distilled initially as gasoline, there would be none of the heavy crude. One gets the additional gasoline by cracking, but this requires heating the oil to 1400 F which requires considerable energy on its own (though some of that might come from burning byproducts such as the coke). One gets some gas also from reforming the lighter fractions, but this requires considerably less power. So the simple answer (reflected in the costs of the different grades) is that the heavier oils require considerably more energy to process, and thus more cost, and so the refiners will pay less to purchase them (provided there is an alternative).
IOW, again, you’re overstating your case.
HTH.
Cheers,
Scott.
@Pch101:
The EPA’s fueleconomy.gov website gives an “Energy Impact Score” for every vehicle which measures the number of barrels of oil used each year. With each barrel being equal to 42 gallons of oil.
Using this it shows that there is a diesel inefficiency, like you wrote. For example, the ML320 CDI gets an EPA combined mileage score of 20 and an “Energy Impact Score” of 19.7 barrels. Meanwhile, a Corvette Z06 has an EPA combined score of 18, but only uses 19.0 barrels. So the diesel is using more oil despite the higher MPG rating.
However, a Jetta TDI’s score of 11.9 barrels beats the Jetta 2.5L’s score of 14.3 barrels. So in that case the TDI’s higher fuel economy looks to be enough to overcome the issues with diesel refinement.
Going off of this score, it looks like the 33MPG combined Jetta TDI uses roughly the same amount of oil annually as the 29MPG combined Honda Civic.
FYI, it’s not a hard-and-fast rule that diesel comes at the expense of gasoline, especially as the light sweet crude gets more dear.
It would greatly benefit you to realize that hydrocarbon mass is more or less conserved in the process.
@Pch101
I get what you’re saying. It takes X gallons of oil to make gasoline and it takes Y gallons of oil to make diesel, and Y > X.
So because of that, the diesel car goes further on a gallon of diesel than a gas car goes on a gallon of gas, since there’s more energy content in a gallon of diesel than in gasoline.
The ultimate question isn’t how many mpg’s you get with diesel vs gasoline, since they’re two different measurements. It’s how much refined oil was used per mile is what really matters.
Now what I don’t understand is, even with the difference in energy content, which is more efficient? Diesel engines or gasoline engines?
agenthex:
“Eggsalad’s processing also probably results in a very polluting car, even greater than the usual carcinogenic nature of diesel exhaust.”
Processing? What processing? I run it through a 10-micron filter. Explain to me how vegetable oil is more carcinogenic than Diesel fuel, please.
Processing? What processing?
Exactly.
http://www.laweekly.com/2006-07-13/news/the-crisco-kid/
it probably references this, whose study link is broken
http://www.dft.gov.uk/rmd/project.asp?intProjectID=11610
I seriously doubt whatever podunk backyard operation is testing emission properly with their combination of viscosity solution and whatever car they’re using.
The ultimate question isn’t how many mpg’s you get with diesel vs gasoline, since they’re two different measurements.
You’ve got it. Comparing the MPG of a gasoline vehicle with the MPG of a diesel vehicle makes no sense. It’s reasonable to compare gas to gas and diesel to diesel, but they are different fuels with different characteristics and comparing them directly with each other is misleading, as this discussion makes clear.
It’s how much refined oil was used per mile is what really matters.
Mostly true, although because oil contains both gasoline and diesel, we may as well use both (which we already do.) It would be truly wasteful if we were to throw away gas or diesel due to overproduction of one of them at the expense of the other, but we aren’t doing that and probably never will. (We used to back during the 19th century, but today, we extract value from everything in a barrel of oil, from asphalt to jet fuel to gasoline.)
From an efficiency standpoint, the gas vs. diesel discussion is obviously misunderstood by the average diesel fan. Diesel really is slightly more efficient due to the higher compression of diesel engines, and it often is in the real world because of the widespread use of turbocharging. But the MPG argument is obviously bogus, and the turbocharging benefits can be gained in a gas engine just by installing one.
Um. While this discussion hasn’t yet descended into outright flaming, the tone has degraded in those who feel, burning in their breasts, perfect knowledge and who come to smite the sinners. One of the outstanding characteristic of the participants in this discussions on TTAC is the immense span of their experience and knowledge. Everyone here has something to learn, something to contribute. One characteristic of the truly wise person is that he or she is truly inquisitive, even somewhat humble in their knowledge…because understanding evolves and new facts or at least nuances between facts involved constantly emerge. And:
= even Nobel laureates can be looney tunes about their own private hobby-horses, as Pauling was about Vitamin C.
= On the web, as in the Bible, you can find justification and “facts” to fit any understanding or belief.
= when a discussion gets too hot, the wise people leave…Never argue with a fool and all that.
Here’s one of my understandings:
Set aside the matter of energy content of gas and diesel, the Diesel engine is inherently more efficient than the Otto engine as a matter of thermodynamic realities.
Ha! I knew it, we’re all misinformed. According to elsewhere on the net…
Unfortunately, it was not Rudolf Diesel who invented the ‘diesel’ engine. Herbert Akroyd Stuart, an Englishman, built the first ‘diesel’ engine in 1890 and had a patent on the design. Diesel did not actually build any engine until 1897, and this ran on coal dust, was quite different from what we call a ‘diesel’ engine today, and actually blew up and nearly killed him. By contrast Akroyd Stuart with the company Ruston Horsnby had been building engines and ‘diesel’ powered tractors for several years before Diesel built his first
So it’s a Stuart engine, yet another Limey invention.
Set aside the matter of energy content of gas and diesel…
Being that’s a critical point that diesel fans must ignore to feel content with their arguments, there is no reason to set it aside.
As noted, diesel does have the advantage of higher compression. But the MPG argument needs to be torpedoed for the fallacious indulgence that it is. Every time I read it, I wince, as it is obvious that the people making it don’t understand it.
Diesel fuel packs more energy into a quantity of fuel, consuming more oil in the process. If you don’t understand the implications of this, then you will be missing most of the equation.
I’ve have had 6 VW diesels back to a 82 Rabbit. One thing that is over looked is the life of a diesel engine. I’ve never got less than 300k+ out of one & sold them for over 1/4 of my purchase price. There are no plugs,wires,etc to change & change the oil they’ll run forever. I didn’t want to even mention converting them to used veg. oil & drive for free.
bstainbrook,
those Toyota Corollas from the 80’s last 500K miles without problems, too. The engines today are just great, no matter if they’re gasoline or diesel.
What I have been trying to get through to Pch101 et al is that the Diesel engine is inherently more efficient than an Otto cycle engine. If there was a some perfect fuel that would both vaporize nicely for the Otto AND not pre-ignite in the Diesel, thus it could be run in BOTH Diesel and Otto engines, you would get better MPG from the Diesel than the Otto.
I know very well that Diesel has more energy content than gasoline and regard that, given Diesel’s near price parity, a double reason to run Diesel: #1 Higher Thermodynamic efficiency #2 Greater energy content. Like a Certs breath mint…but not smelling quite so mice.
But of course, for Pch101, gasoline is the more righteous fuel, so none of that matters, and those that appreciate the Diesel are fools and mountebanks
What I have been trying to get through to Pch101 et al is that the Diesel engine is inherently more efficient than an Otto cycle engine.
Yeah, it’s like 5-10% more efficient based on what I’ve seen of BSFC numbers assuming similar level of tech/cost in engines. Big deal.
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I know very well that Diesel has more energy content than gasoline and regard that, given Diesel’s near price parity,
Why don’t you read the link and comments you posted yourself from the Oil Drum to find out how the petroleum derivatives are created. The reason why it may be off from hydrocarbon per $ price parity has more to do with refinery design/mix and market demand for light oils in addition to diesel.
Density matters because one of the fundamental arguments for diesel is using less oil. Well you don’t use less oil just because you can fit more of it into the same volume for storage.
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gasoline is the more righteous fuel, so none of that matters, and those that appreciate the Diesel are fools and mountebanks
They can’t seem to understand very basic arguments, so make your own judgment as to how smart they are.
One characteristic of the truly wise person is that he or she is truly inquisitive, even somewhat humble in their knowledge…because understanding evolves and new facts or at least nuances between facts involved constantly emerge
I made the casual remark on density towards the very top of the comments. Thus far, I’ve seen nothing on mass density vs. energy density vs. specific energy yet. I’m actually kind of curious how much the discrepancy between the former and latter ratios for gas/diesel is a matter of base chemistry of hydrocarbon length or practical combustion realities. Where are these nuances you speak of?
Ok, to answer my own question, the specific energy is being measure for complete combustion w/ O. So for same mass of hydrocarbon’s, diesel should get 3-4% more energy anyway. That means their thermo advantage is even less impress given real world combustion results.
agentex, thanks for conceding a 5-10% efficiency advantage for Diesel. As for refining mix, there are many ways to fraction crude, but are you saying there should be some perfect fractionation to do this and we should require the refining industry to follow this perfect model? If so, why would this be perfect and would it be worth the enormous cost to rebuild our refining infrastructure to produce it?
And wouldn’t that be interfering with the free market? In the meantime and in the real world, the higher energy content of diesel is available at near the price of gasoline….though it may be quite a bit higher in neighborhood fuel station that don’t do much Diesel sales.
Anyway, as I understand refining, there is a limited amount of diesel in crude (varies depending on the heaviness of the crude), while you can crack it to make lighter fractions such as gasoline. You *can* do the opposite, namely fuse lighter fractions to make heavier ones, using the Fischer-Troepf process, but that isn’t really done much. So as I understand it, you get a certain amount of diesel from fractionation, but you can adjust the amount of gasoline by splitting heavier fractions (such as Diesel). So in making more gasoline, you are robbing from the Diesel stock. Which is what happens (or used to, when America hit the road in the summer) in the summer. And I *do* realize that everyone can’t switch to Diesel…there isn’t enough of it…though half the new cars in Europe have been Diesels for some time now.
agenthex: Where are these nuances you speak of?. To weasel out on this, I’d make the general comment that every time I’ve taken a doctrinaire chiselled-in-stone position in life, I’ve later found myself wrong or at least not anywhere perfectly right. As for the specific here: my TDI Jetta is a mid-sized car that gets me 50+MPG in mixed local and highway driving…and I don’t see a similar midsize gasser getting more than 35-40MPG. That represents something like a 10-20% gain over the gasser. Good enough.
And if you bring up smaller cars like the Fiesta, I’d match and raise you with the 3 cylinder Lupo which got something like 75MPG
I’d be curious to see if gasser MPG improvements could be made by creating a low revving high torque gas engine. And I’d *really* like to see a Diesel hybrid.
@Stewart Dean :
And if you bring up smaller cars like the Fiesta, I’d match and raise you with the 3 cylinder Lupo which got something like 75MPG
The Lupo 3L was a much, much smaller car than the Fiesta, used exotic materials and thin glass, had a extremely annoying automated manual… but it got a 80 mpg Euro rating.
, thanks for conceding a 5-10% efficiency advantage for Diesel
What? That’s in my first post right up at the top. Look, to help out your argument in the future, you should also notice that gas engines use throttles which decreases pumping efficiency and only tend to achieve max efficiency at around max torque engine speed. You can use these arguments until stratified direct injection (or homogeneous w/ turbo) becomes common. The graphs I used are for FSI with quite generous allowances for diesel.
For example, a simple straight comparison should be for the 1.2 fsi vs the 1.6L tsi both around 77kw, but only the 65kw version of the diesel is available in the polo.
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there are many ways to fraction crude, but are you saying there should be some perfect fractionation to do this and we should require the refining industry to follow this perfect model
Refineries are designed for an approximate ratio. This is why diesel is more expensive in the winter due to market competition for light oils (heating).
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So in making more gasoline, you are robbing from the Diesel stock.
As already belabored many times, hydrocarbon mass is conserved. Any necessary conversion is reasonably efficient. Thus with higher density of diesel, you’re just packing more HC’s into it. HC’s are what you buy in crude, using more of them leaves less of what you just bought left. Thus, any technical comparison needs to be by fuel weight and not volume.
agenthex writes:
You can use these arguments until stratified direct injection (or homogeneous w/ turbo) becomes common.
When will that be? And, just to be clear, are you arguing that (comparable generation) gasoline engines can overcome the inherent advantages of diesels? Hint – diesels are more efficient (even when measured by BSFC) and will continue to be. (BTW, note that the LHV (usable energy per mass) of diesel is only about 1% higher than gasoline.)
For example, a simple straight comparison should be for the 1.2 fsi vs the 1.6L tsi both around 77kw, but only the 65kw version of the diesel is available in the polo.
If trees were made of stainless steel then forest fires wouldn’t be a problem. :-/ It’s a rather academic argument if the engine isn’t available, isn’t it? Why should maximum power be the metric for comparing automobile engines?
Comparing mileage means comparing distance traveled per volume of fuel. In 2004 VW offered 3 engines in the US Jetta wagon with a 5 speed manual transmission. Their city/highway mileage ratings were 21/28 1.8T (premium gas), 21/28 2.0 (regular gas), 31/42 1.9TDI PD. (The 2.8 litre V6 (which wasn’t offered in the Jetta) gave 17/26 (premium gas) in the 2004 Passat Wagon.)
Comparing maximum power developed between gas and diesel engines is comparing apples and oranges. Diesels have a redline around 4500-4700 rpm so gas engines will always have more maximum power for the same displacement (and similar generation). What’s most important for real-world driving is torque in the most commonly used RPM ranges. Picking 2500 rpm for the engines, the 1.8T has about 168 lb-ft, the 2.0 has about 122 lb-ft, and the 1.9TDI PD has about 177 lb-ft. (The VR6, offered in the Golf and GTI, has about 195 lb-ft.)
So, of the engines available for the 2004 Jetta wagon, the 1.9TDI PD gives more torque at usable rpms, and gives substantially better mileage than the comparable 1.8T gas engine.
You can spin it all you want, but in the real world TDIs get substantially better mileage than comparable gas engines.
Finally, remember the Audi LeMans TDI engines. Whadayouknow – they get better mileage and still won!
· The winning car’s average speed over the entire distance was 215.409 kph (133 mph).
· Thanks to the economical Audi V12 TDI engine, the Audi drivers only had to pit for refueling once every 14 laps. The winning car used only approximately 41 liters of Shell V-Power Diesel per 100 kilometers (5.7 mpg) – for a race engine producing more than 650 hp and more than 1100 Newton meter (810 ft.-lbs.) of torque – an extremely low figure.
· In the closing laps of the race the Audi drivers even completed as many as 16 laps on a single tank of fuel (approximately 13.2 mpg). Tom Kristensen was the first driver to achieve this.
HTH, but I figure it won’t change any minds.
Cheers,
Scott.
@grunculus
(The 2.8 litre VR6 (which wasn’t offered in the Jetta) gave 17/26 (premium gas) in the 2004 Passat Wagon.)
The 2004 Passat wasn’t available with any kind of VR6. The 2.8 in the Passad was a conventional V6.
Mirko corrects me.
Thanks. The 2.8 litre mileage number was from the EPA, I just assumed it was a VR6. I’ll fix it.
Cheers,
Scott.
in the real world TDIs get substantially better mileage than comparable gas engines.
Again, those of you who tout the MPG just don’t understand this at all.
The MPG of gas and diesel can’t be compared because the fuels are different! Diesel contains more oil, so a barrel refined to produce a higher ratio of diesel produces fewer gallons of fuel overall. Making more diesel for you takes away a disproportionately higher amount of gas from the rest of us.
MPG is only relevant when comparing like fuel types (gas to gas or diesel to diesel). MPG cannot be used to compare different vehicle types.
Study some chemistry, and this will become more obvious. Just because you purchase fuel by volume does not mean that it makes for a relevant scientific comparison when discussing “efficiency.”
When will that be? And, just to be clear, are you arguing that (comparable generation) gasoline engines can overcome the inherent advantages of diesels?
Absolutely. 5-10% is perhaps noteworthy, but not overwhelming.
Hint – diesels are more efficient (even when measured by BSFC) and will continue to be. (BTW, note that the LHV (usable energy per mass) of diesel is only about 1% higher than gasoline.)
You realize that list is not using any modern gas engine. I noted FSI for a reason.
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Why should maximum power be the metric for comparing automobile engines?
Because it measures how fast a car can accelerate, which is the point of an engine.
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What’s most important for real-world driving is torque in the most commonly used RPM ranges.
That’s why they invented transmissions. BTW, in the future, try to use the relative curves instead of absolute value to avoid embarrassment.
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In 2004 VW offered 3 engines in the US Jetta wagon with a 5 speed manual transmission.
They specifically offer the only expensive gas engine as a performance model, and the diesel with high “mileage” green number for dumb people who don’t understand density.
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Finally, remember the Audi LeMans TDI engines. Whadayouknow – they get better mileage and still won!
You realize they were only really competing against another diesel, right? (and just lost)
If you want to discuss le man technicalities we can do that, but you need to realize this is a nuanced issue surrounding cell capacity (pit strategies) and minimum weight.
agenthex writes, but provides no links:
You realize that list is not using any modern gas engine. I noted FSI for a reason.
The 2008 Orbital engine (Revtech report) seems pretty modern to me. YMMV.
A 1.2 FSI doesn’t seem very comparable to a 1.9TDI PD.
# Performance: 0-62mph in 16.5 secs, max speed 97mph, 50.1mpg
# Tech: 1198cc triple, FWD, 64bhp, 83lb ft, 1143kg, 151g/km CO2
Perhaps you can post some better numbers and some links to support your case?
If not, there’s not much point in continuing.
Cheers,
Scott.
Sorry, I mistyped. The 1.2 tsi is a turbo direct injection. I got some detailed spec data on the powertrain itself at one time, but google is failing me at the moment.
But for simplicity, just assume the euro cycle instead of analyzing BSFC plot, you can compare to same (or lower/slower in this case) power diesel and the economy is still well within range of my estimate. 4.2 l/km (65kw diesel) + 20% or 5.5 l/km (77kw gas) -20% density diff ~= 10% more fuel mass use for engine with 15% more power.