you might look at the ford powerstroke desiel, my father has one, he was getting 17 to 18 around town and around 20 to 21 on the freeway. he just put one of those power chips in it, and now is getting 19 mpg around town and 22 to 23 on the freeway, it now goes like a gas rig and added more torque. will haul anything, he pulls a 22.5' stratos and you'd swear there wasn't anything back there! his desiel gets the mileage and has all the torque that is needed!