I HATE when people talk about gas mileage on the jeep forums I visit, but i'm going to post one too. my 13' Sierra is getting 15.2 L/100 km. about 16 mpg. I drive mostly highway. do you guys get similar numbers? i'm not complaining. but I thought with the 6 speed tranny i'd get better than the old 4 speed, and its not. 5.3l motor. no mods, stock tires. yes I drive to fast. 120km/h (75 mph?) the sticker/factory numbers were a lot better though.