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Hybrids get great mileage, but some leave their owners disappointed because their window stickers promise better fuel economy than the cars deliver.
We analyzed more than 315 cars and compared the results of our own tests with EPA window stickers. While most cars in our study fell within one or two mpg of their official estimates, two groups stood out as not living up to the claims their window stickers' promise. (See our full report on "The mpg gap.")
Here's what we found:
These types of cars are much more sensitive to how they're driven, says Mike Duoba, a test engineer with Argonne National Laboratory who works on fuel economy testing. So the old adage about "your mileage may vary" holds doubly true for these types of cars.
Under those conditions, hybrids and cars with turbocharged small engines operate at peak efficiency, delivering excellent fuel economy. But in the real world, where these powertrains have to work much harder to keep up with higher-speed traffic, their fuel economy drops precipitously. That shows up in our testing.
Updates the EPA made to its test procedures in 2008 capture some of this discrepancy with conventional cars, but not the steep drop-off in hybrids and small turbos.
We've discussed our findings with the EPA, and the agency says it is reviewing its tests and considering updating them.
Meanwhile, what should consumers do? Don't write off hybrids, but consider slightly lowering your expectations. Hybrids still get the best mileage of any cars in many popular car types. Among the best is the Toyota Prius, which returned 44 mph overall in our tests (EPA estimates are 50 mpg).
Shoppers should also consider some of the cars that consistently beat their EPA estimates in our analysis: those with manual transmissions or diesel engines. These cars tend to deliver excellent mileage all the time, not just in the city as most hybrids do.
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