I have a 2004 6.0 CCSB with a 4” lift on 315/75r16s and hand calculated I am looking at 13-13.5 all year long. No matter if it’s highway or city, summer or winter fuel. The truck is bulletproofed and has just about every popular 6.0 mod. Straight pipe exhaust and all that. Is this what everyone else is seeing or should I start looking for a problem?