poor gas mileage

i have a 1982 lincoln continental mark xi that was purchased for a individual locally.i have noticed that the gas mileage seems to be below par,does anyone know the avg i should be getting?also from time to time upon acceleration there is a slight odor of gas upon acceleration,what should i check or replace? the car runs fine except for the poor gas mileage i seem to use a quarter of a tank on short trips of maybe 20 miles or so,any help is muchly appreciated,the cars mileage is 127,000 miles