I average upper 20s(27-28). Winter will drop to around 23-24ish. I would do a plug and wire change. Drop in some fuel-injecter cleaner. Maybe engine restore. Just some ideas. 16-20 is bad, horrible even if you drive it hard. I was getting that until I did a spark and wire change.
Best I ever got with the Zetec is 44. I was drafting my dad in his semi and his team buddy was right behind me. So virtually I did nothing aned just got pushed by the trucks.
