With the slow climb of gas prices here in the States the handful of gas/electric hybrid cars available are enjoying an unprecedented popularity these days. Sales of just the Toyota Prius were up by 152% in April compared to last year spurred in large part by the advertised mileage estimates of upwards of 60 mpg in the city and in some places there are lengthy waiting lists. You can probably imagine what the disappointment must be like for someone who’s waited up to six months to buy a new hybrid only to find out that their gas mileage doesn’t come close to what was advertised.
Wired News: Hybrid Mileage Comes Up Short
Drivers rarely see the actual EPA-rated mileage in the real world, according to John DiPietro, road-test editor of automotive website Edmunds.com. DiPietro says most drivers will get between 75 to 87 percent of the rated mileage, with individual variations based on driving habits and traffic route. “If a new car gets less than 75 percent of its EPA rating, then it should be retested.”
Data from independent product-testing organization Consumer Reports indicates that hybrid cars get less than 60 percent of EPA estimates while navigating city streets. In Consumer Reports’ real-world driving test, the Civic Hybrid averaged 26 mpg in the city, while the Toyota Prius averaged 35 mpg, much less than their respective EPA estimates of 47 and 60 mpg. Hybrid cars performed much closer to EPA estimates in Consumer Reports’ highway tests.
Disillusioned owners are directing their ire at the car companies, but it turns out that these inflated claims may actually be the fault of the EPA and a nearly 20 year old testing process that measures engine emissions, not actual fuel consumption, to determine their estimates on mileage. On top of that the car companies are required by federal law to only use the EPA estimates when advertising the car’s fuel economy so even if they wanted to provide more realistic estimates derived from an alternative method they wouldn’t be allowed to.
“The (EPA) test needs to include more fundamental engineering,” says John H. Johnson, an automotive expert who co-authored a 2002 National Academy of Sciences report on fuel-efficiency standards. “They haven’t been updated to encompass hybrids.”
Johnson says the test was created so that it could be affordably reproduced, not to be as accurate as possible. “It’s complicated to simulate all of the engineering factors in a moving vehicle,” says Johnson, and hybrid cars, which use batteries to assist the gasoline engine, make the task all the more daunting.
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Toyota environmental engineer Dave Hermance says the EPA city test includes 19 stops of at least a few seconds, which take up a “non-trivial” amount of the test and could cause hybrid cars to rate even higher than conventional cars because of their reliance on electric motors. “But I could also make arguments about aspects of the test going the other way, too.” Hermance says that because the EPA uses historical data from 1972, it’s virtually impossible to change the test.Hermance says customers who drive less than seven miles per trip will get fewer miles per gallon, as will drivers who speed. “There’s a huge range of customer behavior and limited resources to collect data, so there’s no perfect test.”
Honda points out they put a mileage gauge on the dashboard of their hybrid Civic which makes consumers more aware of their actual fuel efficiency and that if all cars had this feature there would probably be more complaints about the mileage in conventional vehicles as well which also rarely live up to the advertised estimates.
There are still definite advantages to driving a hybrid vehicle over a conventional one in terms of lower emissions, but the main selling point has been the expectation of more miles for your money.
I know I’ve been looking at possibly switching to a hybrid as we just had our first gas station break the $2.00 a gallon price the other day and my driving habits are such that I would probably actually see better mileage than I’m getting now with my Grand Prix. Better yet I’d love to see cars with fuel cells on the market now. Working in the automotive industry I see prototype hydrogen powered cars all the time and they seriously appeal to my inner gadget geek.
Posted on 05/11/2004 at 02:07 PM 
It’s not at all surprising that there’s something of a backlash against the sticker figures on hybrid cars. You’re absolutely right about it being the EPA’s fault, too. I don’t know if their test measures emissions or consumption (they should agree, as fuel consumed should equate to CO2 emitted, assuming they aren’t blowing lots of unburned gas out the back end), but I do know that the Prius operates in electric-only mode for a substantial portion of the test, and that hybrid cars start the test with their batteries fully charged and their engines already at operating temperature. That’s simply not real-world.
That said, it’s quite reasonable to expect pretty substantial mileage improvement with these things simply because they exploit the best parts of gas and electric motors. Gas engines are most efficient at wide-open throttle, so for any given constant speed, the closer your foot is to the floor, the higher the efficiency will be. With a boost from an electic motor, which has (theoretically) maximum torque at zero speed, and a continuously-variable transmission, a smaller gas engine can be used as the primary motivator. I read somewhere that at a constant highway speed, a Camry V6 is operating at 27% efficiency, while the similarly-sized Prius is running at 37% efficiency.
I lust for a Prius, but right now, it’s hard to top Wild Zeke, my 1989 Civic Si. He gets 38 on the highway, assuming I stay below 75, and burns no oil. He’ll turn 200,000 this year, too.
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