New EPA Fuel Economy Ratings
 

Last update: November 17, 2006 – 9:14 PM

EPA aims to give better estimates of actual mileage
New test criteria are expected to more accurately reflect real-world fuel economy.
Rick Popely, Chicago Tribune

Since the government began estimating the fuel economy of new vehicles 33 years ago, it's been careful to note that actual mileage might vary.
And how, say motorists who don't get the mileage that appears on the window sticker.

The Environmental Protection Agency hopes to curb such complaints in early December when it announces new rules for calculating its estimates. They'll be rolled out beginning with 2008 model-year cars.

Though the new procedures are expected to reduce the estimates 5 to 25 percent, the EPA's boilerplate warning will still apply: Your mileage will vary.

"We are very confident these new values will be more reflective of the real world, but how you drive is still the more important factor," said Margo Oge, director of the EPA's transportation and air-quality division. "They should always be viewed as estimates. We don't want consumers to view them as absolute values."

Dave Warnke of West Bend, Wis., can attest to that. He averages 52 miles per gallon from his Toyota Prius, while his wife gets 42 from a Prius.

Warnke, however, is not complaining.

"It all depends on how you drive it, and whether you get the engine up to full operating temperature," said Warnke, an electrical engineer who was attracted by the Prius' technology more than the mileage.

"The EPA is a set testing condition that allows some comparisons," he said. "After that, you're on your own."

Under the new rules as proposed in January, the city rating for the Prius, 60 mpg, could drop to about 45 on the 2008 model. The Honda Civic Hybrid's city rating, now 49, could fall to about 38. Highway estimates for hybrids will fall about the same as conventional models, 5 to 15 percent. City estimates for conventional models are expected to decline 10 to 20 percent.

The EPA's final criteria might not lead to changes that drastic, but the changes will be the first since 1985, when the EPA reduced city mileage estimates by 10 percent and highway estimates by 22 percent to bring them closer to what consumers said they were getting.

Some observers say an overhaul of the estimates is overdue. Auto and travel organization AAA and Consumer Reports magazine, for example, conduct fuel-economy tests and find the ratings wanting.

The Automobile Club of Southern California, a branch of AAA that runs a test facility, measured on-road mileage in 41 vehicles last year and found that 36 experienced worse mileage than the EPA estimates -- on average, 4 mpg less.

AAA then measured mileage the way the EPA does, running city and highway driving simulations in a laboratory. But AAA included three EPA emissions tests that reflect more aggressive acceleration, running the air conditioner and starting a cold engine in sub-freezing temperatures, all of which hurt mileage.

The results came within 1 mpg of the on-road mileage AAA actually recorded.

"With the old test, it was almost impossible to get the EPA ratings," said Steve Mazor, manager of AAA's auto research center in Diamond Bar, Calif. "The [new] test is more accurate and a much better predictor of the mileage people will get."

The EPA will incorporate the AAA tests and add other factors in developing the new estimates.

"It reflects the way people drive today," Mazor said of the more demanding regimen.

Consumer Reports, which measures mileage on a test track and public roads, said that of 303 vehicles it has tested over six years, only 29 equaled or exceeded the EPA estimates. In city driving, vehicles it tested typically get much less than the EPA numbers.

"The EPA city cycle is fairly gentle, much more gentle compared to how most people drive today," said David Champion, automotive testing director for Consumer Reports. "City driving today has more aggressive acceleration and more braking than the EPA test."

In addition, because the tests are conducted indoors under controlled conditions, automakers can optimize the vehicles to perform well in the EPA's driving cycles, Champion said. That is especially true with hybrids, which might run primarily on battery power in the EPA test but use the gas engine more in the real world.

According to the EPA estimates, hybrids get better mileage in the city because that is where they use electric power. However, most hybrids tested by Consumer Reports and AAA didn't come close to those estimates, either.

Consumer Reports got 35 mpg in the city with a Prius rated at 60 and 50 on the highway, vs. the EPA's 51. AAA tested six Prius models, and their mileage ranged from 37 to 50 in combined city and highway driving.

Consumer Reports got only 26 mpg in city driving from a 2003 Honda Civic Hybrid rated at 48 by the EPA. AAA tested two 2004 Civic Hybrids, and one got 36 and the other 49 overall.

"Hybrids still get better mileage than other vehicles," AAA's Mazor said. "It's just not as good as people expect."
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It appears the EPA is acquiescing to the fact that most motorists drive like a**holes. :( :thumbdown:

good to know it only takes 22 years for teh EPA to realize that people don't drive the same way that they test the cars, lol.

^^ true that, its a small estimate of what the car's economy is actually capable of.

Consumer Reports can just stay out of the car reveiwing business. They are lame. I've had several beefs with them, and currently, I am am hoping DCX sues them over their crap.

That's the stock EPA defense, but as we've learned here, even that view isn't necessarily accurate.

2 cars can theoretically have very close EPA ratings (e.g. Civic VX and Metro XFi), yet the two cars won't actually see "peak" MPG at the same highway speeds.

Which means in real world driving, they're going to have vastly different FE than their similar EPA figures would lead us to believe.

When people think of "highway" they gennerally think of cruising at 65mph. Most cars at not at there best mpg at that speed.

I would love if the epa listed the max mpg of cars. Like a low speed cruise rating.

Perhaps the EPA might have some sense of credibility if they'd actually measure the amount of fuel consumed through the injectors, instead of estimating the amount of fuel consumed based on the emissions collected and measured.

Further, they should establish a set of uniform standards in certain areas. No letting automakers cheat by running a higher compression ratio to boost up MPG figures, or testing stripped down models and allowing the automakers to tack the results onto heavier luxury models of the same car. To reflect real world driving, they should have cold starts for their city mpg tests as well. Their highway tests should have speeds of 65-70 mph to reflect how Americans really drive on the highways. Other changes are also necessary.

The EPA's new rules are a bandaid to an inherently flawed methodology.

Ok...we all know the EPA doesn't live in the real world! Only an academian can appreciate the measuring of carbon intakes vs. carbon outputs. And yet...they have completely overlooked the bogus power requirement of forcing this treadmill-tethered vehicle through still air! Oh, they still blow air through the radiator core...but a 60 MPH gale? Over the entire width of the vehicle? Not on this planet!

Aero drag IS included in EPA estimates, although it's obviously a calculated, rather than determined through testing while actually on the dynamometer.

On top of existing drag calcs, apparently the new estimates will also factor in new data about the increase in drag experienced in a typical distribution of cross-winds (which effectively increase yaw & projected area as the vehicle moves through the air). They figure this single factor alone will lower combined EPA estimates by 6% over "still air" driving - more than 2x the adjustment for cross-winds in the current formula.

They are also considering the effect of increased rolling resistance that cross-winds cause (since constant steering angle is increased to maintain a straight line down the road).

See pp. 99-100:

https://www.epa.gov/fueleconomy/420d06002.pdf