[Dave B.]

What Stealthee was getting at is that the oil companies change the additives that they add to gasoline during winter months. This is done primarily to make cars easier to start in cold weather. The 'unwanted' side-effect is a loss in fuel mileage due to the winter blend's lower octane. Your car's electronic systems sense this change and tell the engine to use more fuel.

The only other thing that I can think of that that >>might<< cause the lower fuel mileage would be if one or more injectors was sticking. Using a fuel injection cleaner like Lubro Moly's "Jectron" (my pick) or Sea Foam's "Motor Treatment" in the gas tank should remove any 'varnish' build up in the injector tips. Neither of these treatments will harm your engine if used as directed.

Most of us who have driven for years, however, have just come to expect lower fuel mileage in the winter and don't worry too much about it.