I have this weird auto allowance that requires me to have a newer vehicle. It cannot be more than 2 model years old. My Silverado is smoking like crazy on start up. I add oil but do not want to spend money on oil changes that will not benefit me. I put on about 25k miles a year. At 75k the truck will be traded in. I figure one change a year would get me by. At what mileage would a engine fail because of no oil change?