Basing from the description of your car I'd say that there's very little here you can do .

A Lancer glxi '97 at 120k mileage is rather old. Maybe you can give it a good tune-up. Automatics always consume more than stick shifts even if they are brand new, how much more for an old one?

If you can sell it and get a smaller displacement second hand, manual type then I think you can be better off.