Should be broken in by now
Bone stock (even the tires) 07 Silverado Classic, 4x4, LT3, Crew Cab, Long Bed, now up to 41,000 miles. Best milage 21 mpg calculated - just over 700 miles on one tank of fuel but I was taking it pretty easy on the way home, what with very few fuel stations open at 0200. New Hampshire to Big Pine Key and back in January (4,000+ miles) with a kayak on the roof and a DR 650SE on the rear bumper - 18 mpg calculated. New Hampshire to Daytona and back (2,600 miles) with an 8 1/2x20 trailer and 5 bikes - 11.8 mpg (left in -13F with a big dose of fuel additive to ungel the fuel). New Hampshire to Big Pine Key and back (4,000+ miles) in May with a 16 1/2' boat - 16.5 mpg. I have seen better than 22 mpg for trips but always mix in enough around town stuff to kill the average before refueling, it will get down in the 14 range with enough cold start, shut off in 1/2 mile type driving.
Bruce
Fuel Mileage Getting Better
Just took a trip (Ga. to Tenn. and back) I didn't speed and no heavy load. 21mpg. to 22mpg. Stock. Check mileage both ways. The average and miles /gallons. I had order a bully dog before the trip. Just entered the program last night will update later.