I'm getting on average 325-350 miles per fill up. Which the fill-up typically is around 20 gallons. Everyone, claims that you get worse mileage with a larger tires & lift...mine has remained the same if not improved a little. I'm running 34" tires and 3 inches of lift.

That being said about every 12-18 months my mileage will dive by 100 miles per fill up. This is easily solved by plugs and wires. Only use factory wires and either NGK or Denso plugs, they make a huge difference. You may also need to look into new coil packs, I had one that was going bad and resulted in really bad mileage.

Good Luck Mark