The Environmental Protection Agency’s current Federal Test Procedure (FTP) for city mileage was originally designed to represent a typical trip on Los Angeles streets. The test– codenamed FTP-72– begins with a cold start from 70 degrees. It then runs for 7.5 miles at an average of 19.6 mph, with a peak speed of 56.7 mph (from a short freeway segment). The EPA Highway Fuel Economy Test (HWFET) starts with a warm engine, runs for 10.26 miles, averages 48.3 mph, and peaks at around 60 mph. Does anyone in the real world drive like that?
Obviously not. By the ‘80’s, the EPA was deluged with complaints that its gas mileage estimates were entirely unrealistic (i.e. hopelessly optimistic). In 1984, the EPA reacted by lowering estimates across the board to “more accurately reflect driving styles and conditions.” The government agency trimmed EPA window sticker stats by 10 percent for the city, 22 percent for highway. This overdue amendment helped consumers feel more confident about calculating their fuel costs (and driving skills).
Thanks in part to the huge discrepancy between the EPA’s fuel economy estimates for hybrid-powered cars and their real world mileage, test procedures have been refined again.
For ’08 model vehicles, the EPA numbers will provide “in use” figures based on a combination of the old tests and new tests. The new procedures will incorporate faster speeds (up to 80mph), greater acceleration (up to eight mph per second), warmer outside operating temperature (including air conditioner use) and colder outside operating temperatures (including heater and defroster use).
The industry fully (and rightly) expects the new testing procedures to lower EPA “in use” mileage estimates even further, especially for hybrid drive cars like the Toyota Prius that benefit from “gentle driving” in the city cycle. Meanwhile, we can still glean some interesting information from the EPA stats.
Although it’s not well known, the EPA keeps two sets of books for public perusal. Pistonheads can scan both the government’s official EPA numbers for all cars certified for the U.S. and the raw test results. But wait; there’s more! The EPA also provides a given model’s engine displacement, engine revs in top gear, inertia weight (test weight for the EPA test) and dynamometer resistance settings.
University of Michigan physics Professor Marc Ross has developed formulas that can crunch the EPA’s dynamometer resistance readings to compute the amount of drag in pounds for speeds between 45 and 55 mph. Working with his equations, a math-minded motorist can predict a vehicle’s EPA gas mileage under a variety of test and non-test conditions.
For example, the 2007 Avalon has inertia weight of 3875 lbs. At 50 mph, with its 3.5-liter engine turning at 1555 rpm, the Avalon generates 91 pounds of drag. Bottom line: the Avalon achieves 39.6 mpg on the HWFET test– as compared to 31 mpg on the window sticker.
The 2007 Five Hundred has a 4000 lbs. inertia weight. At 50 mph, with its 3.0-liter engine turning at 1520 RPM, the soon-to-be Taurus generates 105 pounds of drag. Bottom line: 37 mpg on the HWFET test– as compared to 29 mpg on the EPA window sticker.
Theoretically, the Five Hundred achieves 35.3 mpg at 55 mph, 30.4 mpg at 65 mph, and 22.6 mpg at 85 mph. The Avalon gets 36.2 mpg at 55 mph, 32.1 mpg at 65 mph, and 24.8 mpg at 85 mph.
The Avalon’s lower-profile aerodynamic shape and bigger engine make it more frugal than the Five Hundred. (Five Hundred owners pay a price for Ford’s decision to make the Volvo-based model tall and boxy to attract SUV buyers.) With its smaller engine, the Five Hundred is also slower than the Avalon– which has been slated for not being fast off the line. Both vehicles have tall gearing to aid fuel economy.
Toyota doesn’t use pixie dust or a magic carburetor to get better mileage than the Five Hundred. Toyota achieves better fuel efficiency because of the choices its creators made between looks, room, fuel economy, acceleration and drivability.
With revised EPA testing procedures leading to lowered fuel economy figures, with revised CAFE legislation mandating higher required fleet fuel efficiency averages, the pressure is on for automakers to produce more– and more popular– higher mileage vehicles. Only there’s a loophole.
According to the official EPA website, their new “in use” stats will “not affect the CAFE calculation for purposes of determining manufacturers’ compliance with the CAFE standard.” In other words, the new CAFE averages will continue to be based on the old EPA tests. Well how about that?
I did read somewhere that the gas guzzler tax would be applied based on the new rules, which has some carmakers miffed.
What kind of fuel does the EPA use when performing their tests? I’ve often wondered whether they use pure gasoline, or the 10% ethanol blend that most pumps are now serving up anymore.
If the feds are using pure gasoline, then that is one more reason why most of us will never match the EPA numbers.
That seems right why should a company be punished if they make something in compliance with the law (CAFE) with the government specified measuring stick (EPA) at that time. Its one thing to say to companies these are the standards you are going to have to comply with, its quite another to change the way you measure compliance after the fact.
I strongly suspect they use pure gasoline.
I also doubt the Gas Guzzler Tax will be based on the new numbers. The manufacturers have worked hard to keep cars above that threshhold. You can’t just move the bar on them with no advance warning.
FWIW, the Five Hundred is about to get a larger engine and a new/old name.
For the results of my site’s real-world fuel economy survey:
http://www.truedelta.com/fuel_economy.php
I also read something about the targets and methods being revised, does the legislation have provisions for revising the targets and changing the testing methodology, and if so over what kind of consultation period ? These stats only make use in the context of the legislation anyway, nobody should believe this is what they will get with their own car. For that ask current owners.
Surely the biggest encouragement to smaller and more efficient cars is higher fuel costs as recent years have shown. At the risk of starting an OT argument perhaps taxing fuel and using the income to do somethign like provide healthcare may not be such a bad idea after all ? I may moan about fuel costs in the UK but I don’t have to pay for hugely expensive health insurance with infinite “get out” clauses.
And my car averages 52 MPG (imperial) in town ;-)
The Avalon’s lower-profile aerodynamic shape and bigger engine make it more frugal than the Five Hundred.
bigger = more frugal?
z31
As insane as it sounds, it’s effectively true. My buddy’s mid-90s Vette gets somewhere around 30mpg on the freeway. A Vette is the perfect example of aerodynamic shape and bigger engine.
# TaxedAndConfused:
“At the risk of starting an OT argument perhaps taxing fuel and using the income to do somethign like provide healthcare may not be such a bad idea after all”
no no no! Taxes should only go back to where they came from. I’m all for taxing gasoline for road repairs. That way heavy and inefficient vehicles get the usage penalty that all the greenies want, and it helps pay for the increased wear they cause on the pavement. No need for a special gas guzzler tax-the gasoline will take care of that. But healthcare is totally unrelated, and it’s not fair for a commuter to pay for the insurance of a smoker. If you want a healthcare tax, tax cheeseburgers and fries and cigarettes, and tax people that don’t exercise.
Z31:
I agree with Andy. My wife’s 1997 CR-V with a 2.0L, 127 bhp 4 cylinder gets about 24 mpg on the freeway. Because it’s so blocky, and beacuse the engine is underpowered, the motor has to work very hard to push it along through the air. If you looked at a new CR-V, or even the last version, they have significantly higher horsepower, but also get much better mileage. The engine can work at lower revs and can achieve higher real-world mileage.
A major flaw is that EPA test fails to account for wind. For example, my MR2 gets 23-24mpg in the winter, for somewhat short trips – which improves to well above 30 once it gets warm. The O2 sensor sits right under the car because there’s no space to put it in a normal place, so it barely gets warm when you’re driving on wet winter roads at any sort of speed. So the poor thing runs rich during the winter. I bet the nice and cozy EPA testing room didn’t account for that.
By the way, do they account for aerodynamics at all? Seems like the Scion/Element bricks are getting way too good a mileage.
Do hybrids benefit from battery depletion during the (relatively short) test? In other words do they start with a full charge and finish with less?
Interesting. The epa says that my car should get about 32 mpg on the highway, but i get about 40. In the city its about right at 25. Combined I get about 30-32. Interesting article. Thanks.
gas prices might creep close to 4 bucks a gallon area, so good mileage sounds like a good education, and mpg is almost as MS.from laws of economics we know that demand ,supply and prices are dependant on each other.
But by the Jurisb laws there should be an amendment to this- the price of items is regulated by it`s demand – only for those items, that are interchangeable.( if you go and check Snickers bar prices, they haven`t changed a lot in 10 years. why? because they can`t increase prices. for it is an interchangeable( substitute) item, and you can go and buy some other sweets instead, or refuse to buy instead. those items, that are first necessity commodities, increase in price depending on their manufacturers greed and manipulatory power. if gas prices double, you don`t have an alternative for it. so you pay what they ask. the same for insurance, condo rental, etc.so things you can avoid, or are not first necessity, never gain heavily in price, because customers can either refuse to buy , or change to similar usage product.so here we are- 4 bucks a gallon, and still 25 cents a snickers bar.this makes exxon- mobil the biggest profit maker in history of mankind, and the stupid excuses of iran crisis, limited supply or whatsoever are a reason for price increase. so gm makes discounts, rebates, because they are in substitute business, and there is either a japanese company or a bus stop around the corner waiting with jaws wide open.
sorry, I meant those excuses aren`t a real reason for price increse. sorry for being a bit off topic.
Robs right about the bigger motor and slippy shape. a friend’s manual (c5) corvette isn’t that far away from his Prius in real world driving (admittedly without flooring the throttle). Who would have thought a sports car with a big V8 would save the world?
It’s a trade off to a point a 2.0l 4 will get better city mileage than a 3.5l 6 but the 6 may get better highway mileage depending on gearing since the 4 might be at 3k RPM at 60 whereas the 6 might be at 2k RPM.
HEATHROI: “Who would have thought a sports car with a big V8 would save the world?”
TTAC readers, of course!
Alex Rashev:
There is, I’m told, an EPA coastdown test, (how far the car rolls after killing the engine)which gives a rough aero drag figure. That’s then somehow factored into the mpg calculations.
The Scion (xB)/Element do have rounded fronts, if only in plan view, and the “brick” rear can be aerodynamically advantageous, see Wunibald Kamm (Vega Kammback named for him)
I’m sure I’m not the only one here who finds that Consumer Reports’ test loops gives pretty much the same overall numbers they get with mixed city/highway driving. The 44mpg number they got for the Prius correlates very well with my brothers’ 04 vehicle, too.
Of course, YMMV.
That’s good to know. Still, the test is too artificial.
On the note of conserving fuel, the biggest non-nazi thing our government could do to increase fuel economy is to make realtime fuel economy gauges mandatory (like speedometer and odometer). With digital engine management and cost of modern electronics, such gauges will cost pennies, compared to the amount of gas they’ll save. Everyone I know who has one indulges into trying to get peak economy every now and then – which on some cars can almost double your mileage. The driver is a frequently neglected REAL fuel economy variable.
Alex I get a pretty consistent 31 -32 MPG in my XB compared to about 28 -29 in a Corolla
Corvettes only get good mileage under a very specific set of circumstances. You basically have to be coasting in that insanely tall 6th gear with next to no traffic. The Vette’s mileage is heavily dependent on maintaining one set speed. The second you attempt to accelerate the mileage plummets into the teens, if not worse
I’ve had my 06 for about a month now and I think I’ve averaged over 13mpg once. I am living in Boston where both the roads, traffic and drivers are terrible, but I wouldn’t call 13mpg decent by any stretch of the imagination. Then again, I didn’t buy a Vette for fuel economy
Jurisb, there is an alternative to petroleum, at least for those of us with the foresight to be driving a Diesel engine car, namely BioDiesel, or vegetable oil. I’ve been driving Diesels (mostly VWs) since 1982. Starting in 2003 I opted to run my car on anywhere from 10% to 50% home-made fuel made from waste veggie oil. If prices go much higher, I can just run on 90% or 100% of my own fuel.
Mind you this scenario doesn’t scale well, but it can probably grow to cover 15% to 20% of our fuel needs.
BTW I track my mileage at every fill up. The EPA says I should be getting 39/45 MPG out of my Jetta, and I’ve never seen it do less than 47 MPG, ever. My average is probably right on 50 MPG with occasional tanks in the 60s. My last fill up showed 62.2 MPG.
–chuck
“I’ve often wondered whether they use pure gasoline, or the 10% ethanol blend that most pumps are now serving up anymore.”
The EPA test don’t actually measure gas mileage. It’s silly, the normal person would think that they fill up the tank, drive the car under their test and then measure how much fuel was burnt. But what they actually do is measure the emissions while the car is running and use that to extrapolate back to how much fuel is being burnt. So it really doesn’t matter what fuel they use, as long as every car get the same test fuel it all averages out in the end. The EPA test isn’t really to tell you the exact mileage of the car, it’s to give you a metric to compare among cars. As long as every car is treated the same you can use the test to relatively rank cars according to fuel efficiency.
My problem is that it doesn’t really matter how “accurate” the EPA test are compared to real-world mileage. What really matters is that all cars are treated the same. That way you can comparison shop and see which car does better. Granted there are special cases where one car may be better in a certain situation and the EPA says it does worse. But on average the EPA tests are a good metric to show for average driving which cars are better than another. It’s a pain now that they’re changing the test because now it’s going to be hard to compare cars before and after the switch.
indi500fan:
Do hybrids benefit from battery depletion during the (relatively short) test? In other words do they start with a full charge and finish with less?
I often drive the last mile or two of my trip home mostly on electricity. This will lower the SOC (state of charge) of the hybrid battery to something below 50%. When I start the car cold the next morning, the engine has to run for a period of time to complete its warmup cycle anyhow, and during this time, it is typically recharging the battery a bit, so I figure why not take advantage of that knowledge and use more juice at the end of the trip?
But it all works out evenly in the end, anyhow. I’m getting between 45 and 48 MPG in everyday driving with my 2004 Prius, roughly equally split between highway driving around 60 MPG and stop and go rush-hour city street driving.
Highway driving mileage in my Prius is mostly dependent on speed and wind conditions, but this is typical:
At 50, I get about 52-55 MPG
At 55, I get about 50-52 MPG
At 60, I get about 48-50 MPG
At 65, I get about 46-48 MPG
At 70, I get about 43 MPG
At 80, I get less than 38-40 MPG
The faster I go, the more rapid the decrease in gas mileage.
My Scion brick averages 33 mpg and I climb a mountain every day on my way to work. Some tanks have been as high as 35, and I’ve never gone below 31. Actually both of my last two vehicles (Nissan Frontier and Scion xB) have averaged 2+ mpg more than the EPA estimated highway mileage. I don’t drive like an aged grandmother either, so go figure.
I guess my remark about “aerodynamic shape and big engine = good fuel economy” was confusing. The combination of a big engine and tall gearing with a sleek shape can give good performance and good highway mileage as noted by comments about Corvette’s with manual 6-speeds. Of course tall gearing may have drivability issues.
As to reporting better real-world mileage than EPA, if you drive conservatively in warm weather with low wind, you will get better than EPA on account of the 23 percent reduction that EPA had dialed into the window sticker. If you drive faster, the mileage drop will vary depending on the aerodynamics of the car, and not all cars drop the fixed 23 percent, hence the revision to the EPA test procedures — the constant 23 percent correction is not completely accurate even in comparing cars.
As to variables, gas can vary as much as 5 percent in BTU’s/gallon, and some has said that gas should be sold by the BTU (or perhaps by the pound if it doesn’t have ethanol mixed in). The theory is that people can’t measure tank mileage to better than 5 percent anyway owing to driving variations and tank fill variations, so they sneak in gas that varies that much.
As to the effect of wind, I second the remark that in highway driving, wind is the biggest factor, and based on a gas mileage gauge, wind will kill your mileage unless the wind is right at your back with no cross-wind effect. The aerodynamics of cars with cross winds needs more study. Boxy cars will see more drop in mileage relative to EPA numbers from either faster speed or wind.
The EPA test gets aerodynamic and other drag for test cars from a coast-down test between 55 and 45 MPH, a test done by the auto maker. The coast-down test is converted to a mathematical formula of drag (lbs) = A + B*V + C*C*V where V is in MPH and A, B, and C are on the EPA Web site for the “Test Car List Data.” The A coefficient is roughly tire drag, the B coefficient viscous drag in transmission components, and the C coefficient air drag, and I have found that the total drag squares nicely with the reported coast-down times.
But if you look at the numbers for different cars of similar class, the B and C values vary a lot, and I am thinking there is a problem fitting coefficients to the narrow speed range of 55-45 MPH and extrapolating to drag at higher speeds.
There are also holes in the EPA tables where they give the ABC coefficients and sometimes give the coastdown times and sometimes not, and if someone wants to pick apart the EPA test procedures, a person should examine the ABC coefficients and coastdown times, especially for variations between model year of the same car. If someone wants to look critically at the validity of EPA and how EPA doesn’t square with the real world for some cars, the drag numbers are a good place to start.
Zarba:
they have significantly higher horsepower, but also get much better mileage. The engine can work at lower revs and can achieve higher real-world mileage.
That has nothing to do with the displacement. It has to do with more efficient design and better fuel maps.
Correlation does not prove causation.
The point of the Marc Ross report is that the bulk of the cars out there of a particular generation of technology (O2 sensor-controlled fuel is current tech), apart from Diesels and hybrids, have pretty much the same efficiency and fuel-consumption maps. You would think that the Avalon has a more-efficient engine map than the Five Hundred, but the difference is small once you take into account the vehicle drag and transmission gearing.
“greater acceleration (up to eight mph per second)”
Eight mph per second acceleration? There’s plenty of cars out there that can’t accelerate 0-60 in 7.5 seconds (60/8=7.5). For instance the Scion Xbox that has been mentioned more than once in this discussion or the Toyota Prius. What do they do for these cars? As far as top speeds of 80 mph, I only drive that fast when I’m in Idaho (75 mph speed limit) or passing somebody in a 65 to 70 mph zone. And, I drive faster than most of the people around me-I pass more cars than the number of cars that pass me. Doesn’t seem all that realistic to me.
i would love to access and better understand those formulas from University of Michigan physics Professor Marc Ross – i just drove the new cayman last weekend and was surprised to see a mileage claim of 32 highway miles per gallon for it.
wonder what the outcome would be using ross’ procedures?
Lumbergh21> You take that back! My xB can do 0-60 in 5.2 seconds.
When pushed off a cliff. :)
Alex Rashev:
April 24th, 2007 at 10:38 am
… On the note of conserving fuel, the biggest non-nazi thing our government could do to increase fuel economy is to make realtime fuel economy gauges mandatory (like speedometer and odometer). With digital engine management and cost of modern electronics, such gauges will cost pennies, compared to the amount of gas they’ll save. …
Chrysler has had this since the 1980’s. Their trip computer display (not standard but it seems to be included in most vehicles) will re-calc your mileage on the fly every few seconds. It does open your eyes to how driver behavior and road conditions effect mileage. I remember watching it as I sent over a large suspension bridge and used the gas pedal to maintain a constant speed over the entire span. Mileage up to the top of the span – 9 mpg. Mileage down from the top – 80 mpg. LOL! I used to make a game out of trying to keep the mpg number high and constant. Other makers must have similar displays for their cars. Now that I drive a different car I can only guestimate my mileage by tracking my trip odometer and gas receipts.
I think I agree with miked – accurate EPA ratings don’t really mean much to me, as long as vehicles are tested in the same fashion, I could (in theory) use them as a tool to judge fuel economy when purchasing a car – which in a very politically incorrect fashion I’m about to admit – I couldn’t give a hoot about. I figure the car will get what it gets, and there you have it. I’ve never even dreamed that a 1, 2 or 10 MPG difference should factor in my car buying decision.
Yeah…I know – what the hell is wrong with me, huh?
windswords-
I like your observation and agree it couldn’t cost much. I am currently driving (but don’t own)a 2007 Pontiac Grand Prix GXP that has a real-time fuel economy function. By watching the readout you will ‘learn’ what behaviors are rewarded by the best numbers. I am averaging over 24mpg in mixed driving (almost 29 pure freeway) from the 300+ hp 5.3L V8 from what I learned from the Driver Information Center (DIC).
Prius owners make a game out of watching their display and getting the best mpg
In the old days they not only used pure gasoline, but it was a specific blend of gasoline for emission testing that came in barrels (at the time supplied by Chevron), probably has not changed.
The other thing this does not address is how fuel mileage of vehicles varies with age in the real world.
Anecdotal, but I usually kept a GM pickup truck and a little Japaneses car around. When they were new the PU more or less got the fuel mileage it was supposed to and the cars got better in the city and the same or a little worse on the highway.
As they aged the PU’s lost significant fuel mileage relatively rapidly, ie after a year or two it started to get significantly worse and it had nothing to do with the state of tune and they still passed emissions with perfect readings. One has to conclude that it was general wear and tear and the auto gearboxes.
This never happened with the small Japaneses cars even after much longer use, so from a sampling of 20 or so vehicles one has to conclude it either is due to the auto gearboxes or it is characteristic of US made vehicles (also noticed the same on two US made cars owned a long time ago).
To add to Paul Milenkovic’s post on variation in fuel economy, you can also add rolling resistance to that list. The types of tires fitted can impact fuel economy – moving from 225 all season tires to 255 performance rubber on my 330Ci cost me around 2MPG (which is why hybrids come equipped with high tech no-grip rubber). Also factors such as inflation and road conditions can impact rolling resistance. Driving at highway speeds in the rain can also reduces my mileage by as much as 4MPG depending how much water is on the road.
Most hybrids come with regular tires, not “high tech no-grip rubber”.
After they wore down, I did end up replacing the stock Goodyear Integra’s with Michelin Hydroedge’s, because they give better rain handling. I think I did sacrifice 2 to 3 MPG for this decision.
ZoomZoom – the Toyota Prius is fitted with low-resistance Goodyear P185/65R15 tires. This is done to improve fuel economy but the lower the rolling resistance the lower the grip – its one of those ‘there is not free lunch’ inconvenient truths of physics. While I’m all for economical transportation, I think the that sacrificing a cars grip on the road in order to get a couple of extra MPGs is a dubious practice by hybrid makers. You were wise to upgrade your tires.
Gas mileage is interesting, but it’s not the biggest cost for most folks. Depreciation is the killer. Cost of ownership is what you really want to know, and that’s one reason SUV’s and trucks got so popular. Rising fuel prices are changing the equation, but even worse is rising mileage.
Still, I suggest anyone who is tracking mileage also do a cost of ownership study. I think kbb.com still has this info on their site. Recalculate based on your mileage, and realize that if you raise the mileage, you are also increasing depreciation.
My calculations showed me that even with $5 a gallon gas, I was better off keeping my land cruiser than trading for a new sub compact. (While a ten year old ‘crusher is still a nice ride, a ten year old subcompact is generally a heap.)
Here is the real kicker – IT IS THE GOVERNMENT’S FAULT.
Buying a new car means tons of taxes, and, in Colorado, ownership taxes. Tax expenses on a new $20,000 car is more than the entire fuel bill for the first three years!
Everyone knows milages is a poor indicator of real world performance.
Interesting thought: How about a TTAC Milage Standard or Test procedure?
“Chrysler has had this since the 1980’s. Their trip computer display (not standard but it seems to be included in most vehicles) will re-calc your mileage on the fly every few seconds. It does open your eyes to how driver behavior and road conditions effect mileage.”
I’ve seen those gauges, and they’re neat but I don’t think all but the most observant people are going to use that to save fuel. I agree with the original poster who said it would be a good idea to have real time fuel mileage gauges because it would make people save fuel. But the key is they need to be much more real time than the DCX updates every second. I test drove a BMW 32? a couple of years ago and it had a neat real time mileage gauge. It was an analog dial just like the speedometer. When you stepped on the gas the needle would dive towards 0. That’s the kind of feed back people really need to save fuel. The kind that updates every couple of seconds doesn’t really give you the feedback you need to know to stay off the gas.
It would be a real cheap and easy gauge to add too. I’m working on a homemade version for my ’89 4runner (pre obd-ii where all the data is easy to get). All I’m doing is taking a reading from the ECU every time it pulses the injectors. By knowing the pulsewidth of the injector and the vehicle speed, a simple analog circuit can make a voltage proportional to your fuel mileage and then that goes to a simple gauge to display the mileage. It’s a very high bandwidth measurement – it will update every injector pulse which is once every two engine revolutions. So you get near real time output. If a complete hack like me can do it, it’s trivial for car companies to do it too.
Yup, the analog gauges would be great. Especially if you could do it with two (or even three) needles – one for immediate feedback and one for trip average that gets reset every time you reset the trip odometer.
Oscilograph-type digital graph would be best, but I bet it would cost more.
Still, even a digital display is better than nothing.
While we’re talking about two-needle gauges, a two-needle tachometer on entry-level stick cars would be awesome (one for engine and one for transmission input shaft RPM’s). If it saves one burned clutch for each 100 gauges installed, it’ll be worth it.
I’ve never had a problem with the EPA estimates. My record in the old 95 Integra GSR was 37 mpg (epa highway is 31) and with an 01 Corolla it is 42.5 mpg (epa says 41 highway). Then again, I don’t use the AC, I drive the speed limit (65 on the interstate), and I use a manual transmission combined with a lot of tricks to get better mileage. It’s actually kind of fun, and you get a nice little reward for it when you fill up at the fuel station.
TTAC mileage test
full throttle acceleration to 80mph
stomp on brakes
repeat several times
write down fuel economy on slip of paper
toss slip of paper in wastebasket
return to automotive enjoyment
Seriously, one of the things that impresses me is how far my car goes on coast down with clutch disengaged. The tires are at 37/44psi front/rear per spec. Let one go down 5psi and it does matter to handling. Why aren’t more cars equipped with relatively high pressure tires? Can’t active suspension firmware compensate for the harsh ride?
Hey all. I have to jump in here and say that both cars I’ve owned have had both real-time fuel consumption, and long-term average readings. My 1985 BMW 325e (5spd) had the analog, real-time MPG needle under the tach (The e30 M3 got an oil temp gauge there ;0) ). My current ride, a 1993 Saab 9000 Aero (5spd) has a real-time bar graph (5mpg increments) which is updated multiple times per second and sits below the speedo and tach. Both cars have average MPG displays which can be reset when you (a) re-fill the tank, (b) start on a long trip, or (c) start down a very long grade and want to see it read 99.9MPG; that is to say, you can reset it when you’d like. I find that both were a bit optimistic (3-5%).
My 2.3L turbo-charged four (225HP, 258 lb-ft @ 1900-5000 rpm) gets right at 30MPG. That figure was determined after filling it up with 17 gallons +/- after 517 miles, not based on the computer, which read about 32 MPG. Longest single tank was right at 525, but I don’t make a habit of running it dry.
I think the gauges are nice, but, as another poster mentions, only the most observant of drivers will change their driving habits. Those persnickety drivers are probably the ones who already are careful about their driving anyway.
Happy driving.
“one for engine and one for transmission input shaft RPM’s”
The only time these two are different are before the torque converter locks up. And unless you’re driving a Diesel pickup where the computer locks and unlocks the torque converter to give you 1/2 steps in your gears, the torque converter is generally unlocked below 35mph and locked above. It wouldn’t be too useful of a gauge. You could just have an idiot light in there that told you when the torque converter was locked.
If you’re driving a stick and have this gauge, those needles better be in the same position all the time or you’re doing serious damage to your clutch.
Anyone who relies on the government to give them accurate gas mileage estimates for their vehicle deserves the disappointment most will experience.
Thank-you.
“Prius owners make a game out of watching their display and getting the best mpg ”
In an effort to justify their rather large monthly payment for such a small, basic car :)
Torque is what gets you better milage out of larger displacement engines and diesel cars. The ability to turn a big gear at low RPM is what matters.
In an effort to justify their rather large monthly payment for such a small, basic car :)
Careful, some here will retort that a Prius is a fairly large car, and that they are loaded with things like Navigation, neato computers, and other doo-dads that a ‘basic car’ would lack.
I’m just sayin’
Here is my FWIW, every car I have ever owned has almost always returned mileage that was pretty consistant with the EPA numbers for it, if not better. A few examples…my 1987 Cutlass Supreme with 3.8 engine constantly averaged 18 city and 25 hwy. And I drove that car in my early 20’s, and even though I maintained that car well, I really “drove” that car. Often times though, I can do better. There was a time a few years back drove my mother’s 2000 Taurus SEL with the duratec engine from Tawas City, MI to Sleeping Bear Dunes, across the state, and back one one tank of gas, and averaged 32 MPG, the car was only rated to get 28 hwy. And more recently I drove my ’04 Olds Alero (V6 auto) to Florida and back and while traveling through the mountains in Kentucky and Tennessee I averaged 32 mpg, and that even included sitting in a traffic jam in Knoxville…the car is only rated to get 29. So I guess what I am getting at is that it’s not that hard to get the same numbers the EPA gets. It’s too bad that they go through all that trouble to come up with the same numbers I get just by filling my tank up and calculating my mileage…so go figure :)
Alex Rashev–
You put an oscilloscope in my car and I’ll be dead in a week.
While we’re talking about potentially distracting gauges, it would be neat to have a stopping-distance-to-zero gauge in addition to a speedo. And if you had the proximity sensors of the new generation of adaptive cruise control, you could have a second needle on the same dial that told you how close you were to hitting something. Might not be useful, but it might be kinda fun.
Miked – that’s for manual transmissions only. Main purpose is that it allows you to match your upshifts/downshifts without having to guess or do hasty speed/RPM calculations :) Also tells you when you’re going fast enough to release the clutch fully. Trust me, studen drivers will appreciate it.
BTW, if I had a dollar for every time a person that I was teaching to drive stick would burn, drop, or otherwise abuse the clutch in gears other than first, I’d be rich. Instead, I have a nice annual clutch replacement bill :)
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As for gas gauges, many people do watch them. I had one in my Subaru, at first I paid no attention to it and got 12-15 mpg. Then came the gas crunch of 2005, and after spending 3 days on a bicycle because the whole town (!!!) had no premium gas, I noticed that this little neat display was showing me good things. A month later, I could get 20mpg while still doing 3 second 0-45 runs on every stoplight.
If for every 10 cars sold, two would get a 5mpg improvement, that’s 1 extra MPG overall. Add tire pressure monitors with an alarm, and you have another MPG (deflated tires kill mileage big time).
That’s 2MPG for MAYBE $100 a car – pays for itself in the first year of ownership. Best bang for the buck.
some interesting numbers regarding the scion xB and Cd
* 0.7 to 1.1 – typical values for a Formula 1 car (downforce settings change for each circuit)
* 0.35 – Dodge Viper GTS )
* 0.45 – Dodge Viper RT/10
* 0.42 – Lamborghini Countach, 1974
* 0.38 – Volkswagen Beetle
* 0.38 – Mazda Miata, 1989
* 0.372 – Ferrari F50, 1996
* 0.36 – Ferrari Testarossa, 1986
* 0.35 – Scion xB, 2004+
* 0.32 – McLaren F1, 1992
* 0.310 – Lamborghini Diablo, 1990-2001
* 0.29 – Porsche 997 GT3, 2006
* 0.27 – Honda Civic Hybrid, 2006
* 0.26 – Toyota Prius, 2004 – 2007
* 0.25 – Honda Insight, 1999
* 0.117 – Summers Brothers Goldenrod Bonneville race car, 1965
Torque is what gets you better milage out of larger displacement engines and diesel cars. The ability to turn a big gear at low RPM is what matters.
Don’t forget that diesels have the benefit from the absence of a throttle (as do some recent BMW gas engines).