Consumer Reports: Overstating gas mileage [EPA figures on gas mileage are off by huge amounts]

wfaa.com ^ | September 20, 2005

[grundle]

http://www.wfaa.com/sharedcontent/dws/wfaa/daybreak/consumernews/stories/wfaa050920_wz_crmpg.769b7aa2.html

Consumer Reports: Overstating gas mileage

07:22 AM CDT on Tuesday, September 20, 2005

Consumer Reports

When shopping for a new car, the gas mileage is a top priority these days. Automakers' mileage predictions are based on lab tests like the ones conducted by the Environmental Protection Agency.

Cars are strapped onto a machine called a dynamometer. It turns the front wheels while a computer directs the driver to speed up and slow down.

Consumer Reports just analyzed the fuel economy data of every vehicle it has tested in the last five years. CR's Kim Kleman says this analysis reveals the mileage for 90 percent of the vehicles is overstated.

"The EPA tests don't correspond to the way most of us drive," Kleman said. "Their tests represent driving on a 75-degree day on a road with no curves or no hills, which is ideal for maximizing fuel economy."

The EPA tests haven't changed in 30 years, so they don't take into account today's driving conditions. There's a lot more congestion, idling in traffic, and widespread use of air conditioning.

Consumer Reports runs its own fuel economy tests. The engineers say these tests—done outdoors—give a much more accurate assessment of the actual mileage you'll get from a car.

Consumer Reports' tests often turn up results that are substantially different from the EPA's—especially for stop-and-go city driving.

For instance the EPA says you'll get 22 miles per gallon with a Jeep Liberty diesel, but Consumer Reports found you'll get just half that—11 miles per gallon.

With a Chrysler 300 C, the EPA says you'll get 17 miles per gallon, but Consumer Reports' tests get only 10.

As for a Honda Odyssey minivan, the EPA gets 20 miles per gallon; Consumer Reports gets just 12.

The differences Consumer Reports turned up with hybrids in city driving are even greater. The EPA says the Honda Civic hybrid gets 48 miles per gallon; Consumer Reports measured just 26.

"Newer cars tend to overstate the mileage more than older ones," Kleman said, "so the discrepancy between what you're promised and what you're getting seems to be growing."

Consumer Reports says with skyrocketing gas prices, that's a trend that's more troubling than ever.

[wallcrawlr]

My 1999 Chev Suburban gets consistent 16mpg.

Lets see...if I look up what they claim it was supposed to get...

http://www.edmunds.com/used/1999/chevrolet/suburban/100013043/specs.html?tid=edmunds.u.prices.leftsidenav..6.Chevrolet*

Fuel
Fuel Tank Capacity: 42 gal.
EPA Mileage Estimates: (City/Highway)
Automatic: : 14 mpg / 18 mpg
Range in Miles: (City/Highway)
Automatic: 588 mi. / 756 mi.


To me it looks similar.

[mewzilla]

The last 3 or 4 cars I've owned have achieved mileage remarkably close to the EPA figures. And I don't feather the throttle. Perhaps Consumer Reports is doing it wrong.

Some of it is driving habits. Proper tire inflation is another. Load is still another. Weather conditions. Type of roadway driven. The cars are tested with a driver, new engine, perfectly inflated tires, on perfect roadway in perfect weather conditions. So yeah, mileage might be a lot lower for John Q. Public.

[norton]

Sure glad you didn't pick on the '73 Maverick, I'd have taken issue. (While admitting mine's a bit altered).

A note to the "mine gets what EPA says it gets" crowd, I had the misfortune of renting a Lexus something or other last month and it got the same mileage on the highway as our Explorer - and well below what I got from a '67 Falcon V-8.

[Blueflag]

I see your points. I'll grant you that rules drove design.

Now about this ... "The resulting vehicle is taller and more unstable that it otherwise would need to be. This makes them more inefficient that they would otherwise need to be."

A taller/higher vehicle with a higher center of gravity AND a higher roll center will always be a vehicle that cannot generate lateral acceleration equal to a vehicle with a lower CG and lower roll center. That's the physics. So indeed SUVs built on a truck chassis are generally less maneuverable than comparably sized 'car' chassis. I still can;t grant you the 'unstable' label because the SUVs are entirely predictable and controllable within design limits. "Unstable" as a label implies a deficiency that isn't really there. They are entirely stable enough for their purpose. A Honda Accord is far less stable/maneuverable/controllable in violent or sudden maneuvering than a Porsche 963, but that doesn't make the Accord unstable.

to wit, dictionary.com defines stable as --

1. Resistant to change of position or condition; not easily moved or disturbed: a house built on stable ground; a stable platform.
2. Not subject to sudden or extreme change or fluctuation: a stable economy; a stable currency.
3. Maintaining equilibrium; self-restoring: a stable aircraft.

An SUV can be labeled as less-stable than _________ (pick your sedan), but not unstable.

Also being less stable does not make them inefficient. Can't locate any cause and effect there ;-) A Testarossa is far more stable than my niece's Honda, but grossly more (fuel)-inefficient.

REM: I agree that a fully unregulated environment would produce different and better vehicles.

[meyer]

Some of it is driving habits. Proper tire inflation is another. Load is still another. Weather conditions. Type of roadway driven. The cars are tested with a driver, new engine, perfectly inflated tires, on perfect roadway in perfect weather conditions. So yeah, mileage might be a lot lower for John Q. Public.

Can't speak for others' driving habits, but I drive briskly, and I believe in the "over 9, pay the fine rule" (that is, I drive about 8 mph over the speed limit in most places). Terrain around here is very hilly, borderline mountainous. It's part of my every-day driving.

The new engine used in the EPA test should get worse mileage than one that has a few thousand miles on it - that's been my experience anyway. As for tire inflation, that is a significant factor, but you'd have to be running at about 10 PSI to get the results that CR got. I'm not very trusting of the EPA in general, but I'm even less trusting of Consumer Reports. The friend of Nader is my natural enemy, and I believe that they have alterior motives whenever they touch a car.

[par4]

Cars are strapped onto a machine called a dynamometer. It turns the front wheels while a computer directs the driver to speed up and slow down

And here I always thought that the car being tested turned the dyno, now I find out that it's the opposite. No wonder the mileage estimates are so high. I'll bet that the rear wheel drive models have some fantastic ratings.

/sarcasm

[meyer]

If an SUV is unstable, what classification should be given to a motorcycle?

[kevkrom]

The EPA on my new Camry says 22 city, 32 highway. In the two months I've been driving it on my 30-mile (each way) comute into the DC area, I'm averaging (according to the trip computer) about 29.5 MPG. Now granted, I usually avoid the worst of rush hour and the weather here has been quite warm and dry, but I've seen similar things in previous vehicles I've owned, where my commute milage falls on the high side of the city/highway difference.

[NotJustAnotherPrettyFace]

I live in the burbs, got a 2003 Saturn Ion in recent weeks and am getting around 22-25 mpg.

[Frankss]

Have a 2003 Grand Marquis, The sticker on the window said 27 mpg highyway, never seen it! I get 24 mpg highway with aircondition off. Turn on the air and it goes to 20 mpg.

[Fresh Wind]

To get better mileage, I only drive downhill wherever I go.

You can get the same effect by jacking up the rear end of your car. That way you are going downhill no matter what the road is doing. Drag racers have been doing this for years.

[NotJustAnotherPrettyFace]

Straight out of the NY Times:

Wary of High-Voltage Batteries, Rescuers Study Up on Hybrids - 9/18/2005

[NotJustAnotherPrettyFace]

Firehouse.com's University of Extrication - Special Feature - Hybrid Vehicles - Part 3 - Emergency Procedures

[Blueflag]

Donor carrier ;-)

[gridlock]

It is quite safe to drive an SUV, as long as you remember what you are driving. I don't mean to say that the class of vehicles is deficient by design. But, from a stability and safety point of view, they would be better if CAFE did not mandate the rear load floor had to be two feet off the ground.

But I used to voluntarily drive around in a Citroen Duex Cheveux, half the time loaded to the gunwales with God-knows-what. You want to talk about unstable!

[Disambiguator]

If an SUV is unstable, what classification should be given to a motorcycle?

It's funny you mention motorcycles. Consumer Reports stopped testing motorcycles a few years back (probably some time during the 70s), saying something to the effect of "they're so dangerous that no-one in their right mind should own one."

[meyer]

It's funny you mention motorcycles. Consumer Reports stopped testing motorcycles a few years back (probably some time during the 70s), saying something to the effect of "they're so dangerous that no-one in their right mind should own one."

Given the price and availability of gas (especially post-Rita, I suspect), I may just be crazy enough to get one myself. If CR doesn't like it, then I do. :)

[jiggyboy]

It looks to me like wind is not simulated in the EPA tests; dunno how big a factor that is but I know that the formula for wind resistance goes up by the *cube* of the speed.

[mewzilla]

Well, FWIW, we drive compacts and the mileage has always been a couple of miles within the advertised. I suspect the problem is mainly with the gas guzzlers, and we wouldn't buy one of those anyway :) In any case, it's still buyer beware, though folks who don't keep their cars well-maintained are shooting themselves in the foot. Can't blame Detroit for that.

[meyer]

It looks to me like wind is not simulated in the EPA tests; dunno how big a factor that is but I know that the formula for wind resistance goes up by the *cube* of the speed.

I think that they might calculate it in somehow. My 4WD Explorer was rated at 16 city and 19 highway (full-time FWD, no way to disengage the front hubs) and that's what I got. Likewise, my Escape gets within 1 mpg of the ratings for each type of driving. I keep records of my mileage as its a good indicator when something is going awry.