Do you know your car's true mpg?

Recent Consumer Reports tests found some cars got 40 to 50 percent less fuel economy in city driving than the Environmental Protection Agency estimates. The EPA said it plans to come up with new estimates later this year. The adjusted figures will take into account the stop-and-go driving we do on today's congested roads, as well as the drain caused by accessories we love. But Dianne Whitacre at The Charlotte Observer points out the "only way to find out your car's gas mileage is to keep your own records." Alternatively, many vehicles offer built-in fuel economy tracking systems.