I believe the miles per gallon ratings are actual CAFE ratings. In a 1981 AMC color catalog, AMC mentions that the 81 Eagle, equipped with a 4 cylinder, and 4 speed, gets a whopping 29 miles per gallon. In AMC annual report to stock holders......this was mentioned also that it was 2 miles per gallon more than what government required. I don't remember what the requirements were for a 258-6/AT of which what most Eagles were. So as mentioned down below (or above) a Eagle with four cylinder and 'five' speed could easily get 32mpg....on the highway.
From own experience....my 81 Eagle station wagon is a 4 cylinder, 4speed and gets about 24-27mpg here in Houston, Texas when I drive it. At first I thought gas gauge busted as it never moved. I'm used to 390s and 401s you know.
Eddie Stakes