You can view the list of cars here
The program is primarily designed to stimulate the economy, with other supposed benefits in terms of reducing greenhouse gases. Owners of older cars get either $3,500 or $4.500 when buying a new car, encouraging the purchase of new cars.
But if you were even mildly gas-millage conscious early on, forget it, you won't get anything. It only rewards those who bought gas-guzzlers: the EPA spent a month evaluating 30,000 vehicle models made between 1984 and 2004, and decided that only about 8,000 qualify, the ones getting 18 miles per gallon or less. For instance, the Toyota Camry got too many miles per gallon. Ford Taurus sedans, except for some with V8s, don't qualify, but if you happen to have a Ford Taurus wagon, there are some models in some years that qualify. Among cars made in 2004, there are only six models listed as eligible -- all of them trucks or SUVs.
Especially odd is that it does not really matter how big of a difference in gas mileage between your old and new cars. Replacing an 18 mpg car with one that offers 22 mpg, gets you a subsidy. But you cannot get a subsidy if you replace a 19 mpg car with one getting 42 mpg.
It will make the country poorer to subsidize the purchase of new cars, but if it is to be done, it ought to make some kind of sense. If improving miles per gallon is the goal, a sliding scale that varied the subsidy with the difference in miles per gallon between the old and new cars would seem reasonable. If emissions from older cars is important, the subsidy could also be larger when trading in older cars.
There are many other weird details of the program. one is that used cars worth more than either the $3,500 or $4,500 subsidies are not eligible. Essentially rewarding people who have held on to old, cheap gas guzzlers very long, but do we want to reward such behavior? The thought enters your mind: if I buy a new car today with a low gas mileage, might I qualify a decade from now for a similar subsidy program?
And the weirdest is saved for last: the subsidy is only given if the old car is destroyed. Yes, that is right: the cars are to be destroyed. Well, destroying cars at taxpayer expense might be a "stimulus" for the automobile makers and the auto unions. But it simply means that money that would have been spent on other items is now being spent on cars. What is next? How about smashing windows in old houses? After all, newer windows tend to have better insulation and we could generate some new jobs in the window-making industry. Oh, wait, we forgot, there is another program that subsidizes the replacement of home windows.