So this is interesting

You might qualify for up to $4,500 toward buying a more-fuel-efficient set of wheels if Congress OKs a 'cash for clunkers' bill.

By Catherine Holahan
MSN Money
Uncle Sam is dealing. A "cash for clunkers" proposal making its way through Congress would offer the owner of a gas-guzzling car or truck as much as $4,500 toward a newer, more-fuel-efficient vehicle.
Under the bill that passed the House on May 5 and a similar version under review in the Senate, qualifying clunkers must get 18 miles per gallon or less.
If the new car got 4 to 9 miles per gallon more than the old one, going by Environmental Protection Agency ratings, the payment would be $3,500. If the new car got at least 10 mpg more, the vehicle owner would get $4,500. For light trucks, the mileage gain would have to be at least 2 mpg for the $3,500 payment and 5 mpg for the $4,500.

http://articles.moneycentral.msn.com/SavingandDebt/SaveonaCar/Cash-for-your-gas-guzzler.aspx