I go to school in an area that's hilly but my gas mileage seems to be ridiculous.

I'm getting around 12 mpg when I normally get 20+ in a more flat area. There are lots of stop lights and uphill/downhill areas but I'm not sure if the gas mileage should be *that* bad.



I have a 1991 740 GL. Is this really how bad my gas mileage should be in a hilly area? Does anyone else live in the mountains or areas like that?