On Jan 19, 2012 I picked up my '12 CCSB Lariat and was immediately impressed with everything except the fuel mileage. The truck has the factory 20" wheels with the 34" tires and 3.55 gears. Stock I was averaging 16.8 mpg hand calculated, which isn't horrible but my 05 Sierra 1500 with 33's was seeing 16.5 hand calculated, so I was slightly disappointed.
360 miles later, I pulled the trigger on a Spartan Tuner and 4" DPF delete. With the delete and tuner I was seeing 22.1 average highway mpg hand calculated and 18.4 mpg mixed hand calculated. I was much more pleased with this and happy I went with the tuner.
Over Spring Break I finally got a chance to haul my race trailer down south. I pulled my 8.5x20 haulmark race trailer loaded with 6 motocross bikes, 1 street bike ('07 Suzuki GSX-R 750), generator, pressure washer, tool boxes, gear, and other items totaling 8,100 pounds from State College, PA to Tuscaloosa, AL. Averaged 15.1 mpg hand calculated round trip.
Overall I am extremely pleased with the truck and the fact that it didn't flinch on even the largest of hills while passing cars
If anyone is on the fence about tuning/deleting their truck I highly recommend it. Just be prepared to buy tires, cause the stock ones aren't going to last long