probably 21-22 with a slant six maybe even up to 24 25 if you have a clean air filter, fuel filter, good plugs, wires. if you have a 318 it's probably more like 18-19 depends how much your foot is in it
I got 22 to 25 with mine (slant 6). Wish I still had it. Great car. I was the second and last owner and got rid of it in 1985 (car was 17 yrs. old). The only annoying problems I had with it were the choke sticking when the engine was cold (typical of Mopar at the time), and they designed the lower radiator hose too close to the fan belt. No matter what I did, and I tried just about everything, that damn belt would vibrate just enough to rub on the hose slightly and eventually wear a hole in it. Always kept a roll of duct tape on me for that reason.
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