My 1999 Lincoln Continental has been getting around 14 MPG. I filled the tank this morning, and by the time I got home (Drove around town) I had 3/4 of a tank. From reviews i've read online, people say this car gets good MPG for the engine size (around 20-22 MPG) What reasons are there for this poor MPG? (Air Filter, Gas Type, Etc?) Or is it just from age?