(NEWSER) - The government’s Car Allowance Rebate System—the “Cash for Clunkers” plan—goes into effect today, but it might not be such a good deal for you or the environment, Elisabeth Leamy and Nathalie Tadena write for ABC News. New-car buyers who trade up more than 4mpg in mileage get $3,500; make it 10 mpg and you get $4,500. But you could also skip the credit, buy a perfectly good used car, and save more than $10,000. More»