What is a reasonable expectation of gas mileage on a cj5? Mine does about 12mpg on highway. It is the standard 3 speed with 3.54 gears. The tires are 33×12.50x15. Anyone have some info. I was thinking about changing to a good bit smaller tire, maybe something on 29 or 30 inches high. Will this help? Most of my hardcore wheeling is behind me now. Btw it has the motorcraft 2100 carb.