My Yukon doesn't quite have 1,000 miles on it yet but the fuel mileage is a pleasant surprise to me. It replaced a regular cab '99 5.3 Sierra 4x4 with 3.73's. The heavier Yukon has 4.10's, much peppier than the Sierra and with the same type driving, gets slightly better mileage. 17.5 vs. 18.