It seems lately that everywhere you turn someone is encouraging you to get rid of your car or appliances in exchange for a newer, more fuel efficient or energy saving model. Even with the government rebates, there is still an argument to be made for keeping a clunker though. First of all if your car or appliance is paid in full, you would then be looking at paying cash outright, or financing your purchase with interest when you were already in a good position financially by not having a payment. You may need to divert funds that could already be allocated to other bills or to savings. There are also other factors to consider such as depreciation of a new vehicle, insurance rates, and manufacturing costs.
I’ve read that 25% of a cars carbon dioxide emissions come from the manufacturing process. Since your used car has already gone through the manufacturing phase, it produces no additional environmental demand. Even though it may get less gas mileage, driving it responsibly arguably produces less pollution than purchasing new.