Laudersscotch: you should be getting more than that with your car unless you have an extremely heavy foot. My 84 is similar to yours with 82k on the engine with an auto tranny and I still get about 19 with in town driving. Mind you I don't drive like an old lady either but I'm not flooring it out of every light.
in my 85 n/a auto 88k i would get like 14-17 city and 22+ highway, but in my AE 5-spd 86k i get 20 in the city 24+ on the highway. in both car that flooring it most of the time. the n/a had a complete tune up done recently and i havent done anything to the AE.