Sierra diablew tune mpg gain? Sanders46

[Sanders Overman]

Hey guys just joined this site and picked up my first gmc truck a few weeks ago, loving it so far! It’s. 2015 Sierra 1500 slt with the 5.3, 6 speed auto and 3.08 rear end. I recently leveled the truck and added some 275/60r20 bfg all terrains. Anyways my question is I know I won’t get back to the mpg before the leveling kit and tires, but I have been in contact with lew from diablew tune and I’m interested in his tunes as I’ve heard nothing but great stuff on here. Someone with a similar truck to mine and a custom tune from lew, have you noticed any increase in mpg? Lew told me every truck is different and I understand that completely but would like to hear if anyone has seen mpg gains from his tune? Thanks!

[boettcher40]

I have literally the exact same truck, just a 2014. Leveled with 5100's and same size wildpeaks. I purchased a Diablo i3 tuner last year, and wasn't thrilled with the canned tunes. Talked to Lew quite a bit on future mods, and I pulled the trigger on his custom tune. Trust me when I say, it is completely worth it! It woke my truck up dramatically, and more importantly the transmission shifts so much smoother, it doesn't stutter and try and find a gear when you mash the throttle. 

 

To answer your question, I experienced a slight gain in MPG. Like Lew said, every truck is different. I lost probably 1-2 when I took off the lower valance for more clearance. Then gained 1-2 back from a CAI and the L86 intake manifold and TB. I wasn't really searching to gain mpg with the tune, but I definitely got more smiles per gallon 

[CamGTP]

His downside is the 3.08 gearing. No matter what you do it's always going to be worse off than 3.42's or 3.73's with those larger/heavier tires.

[Sanders Overman]

Thanks for the responses! Boettcher40, do you also have the 3.08 rear end? If so what real world mpg’s are you seeing? And I agree the 3.08 in the rear is not helping me with the larger tires, I’m not so much disappointed in the mpg at the moment as it seems to be better than the 05 f150 with similar tires that I upgraded from, just concerned with cutting off the afm as I drive a lot of 55 mph backroads, and feel like it does help some. Have also heard the 14+ afm was redesigned and seems to be a lot better than the earlier generations so if that’s the case I’m not necessarily opposed to keeping it on