well i picked up a new 2015 sierra slt ccsb 5.3l 4x4 this weekend and love it.. first 100+ mile trip today it registered 21.7 mpg going 75 mph now im wanting a tune my question is are these new di engines responding well to a custom tune? Any mpg difference (good or bad)? Everything is stock and just gonna get a 93 octance tune.. anyone have any baseline vs. tuned numbers im curious as to how much these engines pick up tune only. Btw i love this truck its runs damn good for being completely stock.

 

bump.. also im currently away from my truck and i am about to order the air aide intake tube, drop in filter and a borla muffler to replace the stock muffler and valve my question is does anyone know the size of the factory exhaust pipe? I looked it up and cant find much.. im thinking it would be 2 3/4 or something close to that. 2015 sierra ccsb 5.3l 6 speed 4x4
edit: answered my own question looking a bit further on this forum.

 

Exhaust is 2 7/8" unless you have the 6.2 and these trucks respond awesome to tuning. Tons of torque management.

 

I ran tune only 14.1 on 93 and did E85 tune and ran 13.7.

 

Take it to the DFw truck shootout Able!