That may help somewhat. I think that a full tune up would help, make sure that there's no vacuum leaks, vacuum advance is working properly and correct timing and like I said earlier if it has champion spark plugs, get rid of them. A true but sad thing is that the sbm's are not known for mileage. I had 3 different trucks all of which were 2 wheel drives with 2.73 gear ratio and none of them got more than 13 mpg on the highway, that's just how mopars are, gas hogs.