Really, it would be useful to see some data. Most people, when they purchase a new car, get one with better fuel economy, so we'd think that regardless of the program we'd see an improvement in overall gas mileage. And, the economy appears to be improving--certainly if the stock market is any indication--so its not that big a surprise that car sales are up, again, regardless of the program.
It would be one thing if everything else was down, with car sales up. But that's not the case.
So it appears the government is just giving huge scads of cash to a select group of people with older cars to help them do what they were going to do anyway.
On the other hand, it may be better than some of the other stimuli going on. We'd certainly rather see a few billion go into retiring clunkers, and thus indirectly helping Detroit, as opposed to just flushing billions more down the General Motors toilet hole.
What's galling, however, is the GOP's cynical opposition to the program as some kind of government "giveaway." As you may recall, we had a recession when George W. Bush took office and the GOP took control of the entire government. They had a stimulus program, too. Should've been called "cash for millionaires," as it was an enormous tax cut, the largest part of which went to the wealthiest 1% of Americans.
If Congress wants to put a little more money into the Clunkers program, ok. But this is a program that needs to sunset real soon!