I am proud to say that I drive a fuel-efficient car, a Honda Civic Hybrid that gets as much as 50 miles to the gallon on the highway. My husband's car, on the other hand, is not so green. It's a nearly 15-year-old Land Rover Discovery, and he loves it. According to FuelEconomy.gov, his car gets a whopping 13 miles per gallon and emits 14.1 tons of carbon dioxide each year. We know we need to replace it -- if only for the sake of the environment -- but we cringe each time we think about taking on a new-car payment. Uncle Sam is about to launch a program that seems designed specifically for us. The official name is the Consumer Assistance to Recycle and Save Act of 2009, but it's more commonly known as 'cash for clunkers.' It offers consumers a credit of up to $4,500 if they trade in their gas-guzzlers for new, efficient vehicles. The $1 billion program is scheduled to start soon, perhaps later this week. To qualify, the clunkers must have been built in or after 1984 and be drivable. You have to have owned the car for at least a year and must buy a new car to replace it. At first glance, it seems like a no-brainer -- the estimated trade-in value of the Land Rover is $800. But we had planned to start saving to buy a new car next year. With a little discipline, we would have enough cash to pay in full. If we bought now, we would have to finance a portion of the purchase. So we'd be able to take advantage of the $4,500 credit but might pay more over time in interest. 