Before I bought my 2000 F250 4x2 Supercab LB PSD I did some searching trying to find similar pickups and what their respective MPG may be. Found a few posts but nothing was ever consistent. Also found a lot of "Yeah my 02' CC LB 4x4 with 37's gets 25 MPG!!" Seemed like a load of crap. When I bought the pickup it had 285/75/16's on it. They were Maxxis Bighorn M/T in the rear and Toyo Open County A/T's in the front. I do a 50/50 split of highway and city in hilly terrain. I checked the speedometer against a GPS and was always 1mph faster than the speedo. So using a correction factor of 1.02 ( wont waste time explaining how I figure that buts its close and doesn't change much anyway) I was getting between 14.4 and 14.8 over the course of about ten tanks. NOW I have changed the tires to 265/75/16 Open Country HT tires which are smaller and the mpg range has been 15.5-15.8, with the GPS and speedo in sync. So I saw a solid 1 mpg gain by switching to smaller less aggressive tires. I personally like it better, not just for the mpg gain, but I notice it doesn't down shift as much going up hill and seems to drive a little smoother not lugging those 285s which I dont need on a 4x2 highway hauler. Anyway, thought Id share an honest take on some MPG info.