If you can't get good mpg from a 318, I stand by my first reaction. "You must not know how to tune or drive." If you want to compare compacts or small engines, to a 318 what is your point. I worked on all brands of cars. Mopars were always at the top for power efficiency, and reliability. And I worked on cars when Pontiacs had Pontiac engines, Buicks had Buick engines, Oldsmobiles had Oldsmobile engines, not the cheap Chevrolet junk engines.
Not trying to argue about it. Just stating that I was never able to get good mileage from a 318, I never said that others didn't or couldn't get mileage from them. I do know how to tune I may not be as good as others and I never claimed to be.