I bought a 1980 Ford short step side for mileage so it had 300 six with 4 speed od and it got 15.5 mpg the first tank and dropped to 14 mpg after that. I owned it for about 3 months and it stayed in shop about as much as I drove it. I traded it off and swore I would never own another Ford. 30 plus years later I am still keeping my word. Buy whatever you want but I know what has worked best for me.