I have a 06' F250 CC Lariat 4x4 with 34k miles. It's had the rear main engine seal replaced 4 times and it still leaks. It gets terrible mileage (13 mpg average). It sits on 285/18 BFG AT load E's. Still stock. Stock sucks. I want to bring it to its potential. I love the truck. Don't trust my garage. Need input.