Q: How far off are EPA mileage estimates?

A: Way off, at least according to a series of articles recently published by Consumer Reports. Fivecentnickel.com reports on the consumer watchdog rag's findings that state of the vehicles CR surveyed, 90% got worse mileage than their EPA estimates. In some cases the real world mileage was 50% below the EPA's numbers. The biggest discrepancies could be found in the small hybrid category where city mileage was coming up short by 19 mpg in some cases. CR's suggestion when buying a new car is to reduce the EPA estimates by the following:
Conventional cars and trucks: 30%
Larger hybrids: 35%
Diesels: 36%
Smaller hybrids: 42%