A "cash for clunkers" program made it through Congress yesterday. Starting in August, if you have a car that gets less than 18 miles per gallon, you can trade it in for a cash voucher for a new car. The voucher's value will range from $3,500 to $4,500 depending on the difference between the fuel efficiencies of the old and new cars.A cash for clunkers program is meant to get the most polluting cars off the road and help save Detroit. Some are concerned that this version focuses a little too much on the latter purpose (you can't, for example, use your voucher to buy a used car.) I'm pretty thrilled they could pass it at all-that's the power of the Detroit and environmental lobbies combined, I guess.