Lost MPG after tuning

[Bbaselj]

I searched on here and didnt find much (maybe im just terrible at searching) but I recently tuned my 18 Sierra 5.3 8 speed with the Diablo inTune i3. I selected the canned MPG tune to start and planned on getting custom one later. I also have a Borla Atak and S&B CAI and no leveling kit or lift.

 

With the CAI and Borla Atak I was averaging 18.6 MPG. I tracked this using my 74 mile round trip travel to work for 3 days in a row.

After tuning it dropped too 15.4 (I did the math from trip log and didnt just use the trucks MPG tracker)..same route, temperature changed a bit but my driving habits are the same.

My commute to work is mostly back roads where im doing 55-60 mph.

 

Anyone else ever have any issues with MPG loss after tuning? Everything I read lead me to believe that the MPG would go up.

I'm just more concerned that I did something wrong while tuning.

 

Any help on this issue would be greatly appreciated. Thanks guys!

Edited April 17, 2018 by Bbaselj

[Ryno12]

Are you being heavier on the pedal after the tune?

[Bbaselj]

Just now, Ryno12 said:

Are you being heavier on the pedal after the tune?

I was at first to feel the power difference which was meh didnt expect anything life changing from a MPG tune lol but when I was tracking the MPG the 3 days back and fourth to work I wasn't heavy on the pedal at all.

[Hooper_c4]

Daaamn that's a huge drop. May change my mind on the ol intune afterall

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[Bbaselj]

Just now, Hooper_c4 said:

Daaamn that's a huge drop. May change my mind on the ol intune afterall

Sent from my SM-G930V using Tapatalk
 

Yeah it’s pretty crap. I restored it back to factory and it doing another 3 day test. It got screwed up today from a snow storm and I was stop and go a lot because people don’t know how to drive when it snows lol will post updated results..

[Ryno12]

I’ve got the same tuner & I haven’t noticed an increase in mileage, but I didn’t install the gas mileage tune. Mine has the stock 87 octane tune. Admittedly, I can be a bit heavy on the foot so I’m not expecting any increase anyway.

[Hooper_c4]

You plan on getting should of Lew and having him do his thing? I've heard the preloaded tunes are trash, but I've read that Lew is a genius

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[Bbaselj]

Just now, Ryno12 said:

I’ve got the same tuner & I haven’t noticed an increase in mileage, but I didn’t install the gas mileage tune. Mine has the stock 87 octane tune. Admittedly, I can be a bit heavy on the foot so I’m not expecting any increase anyway.

What about a decrease? After I finish my factory test maybe I’ll install the regular 87 tune. Did you just do the 87 tune preset or did you change some settings yourself?

[Bbaselj]

Just now, Hooper_c4 said:

You plan on getting should of Lew and having him do his thing? I've heard the preloaded tunes are trash, but I've read that Lew is a genius

Sent from my SM-G930V using Tapatalk
 

That’s on the agenda. Just dropped about 2k into my truck so I’m on a break for a bit or the old lady might kill me ?

[Ryno12]

What about a decrease? After I finish my factory test maybe I’ll install the regular 87 tune. Did you just do the 87 tune preset or did you change some settings yourself?

I left everything else the same except I changed the shift to “firm”.

I did this last fall/early winter so the temps were lower & there has been more idle time, so mpg will be naturally worse.

My truck is a 6.2 Denali & I think the mileage computer is averaging 15.7ish over the last several hundred miles. If I baby it or drive conservatively, I can get in the high teens or low 20’s.

[Bbaselj]

Just now, Ryno12 said:

 

I left everything else the same except I changed the shift to “firm”.

I did this last fall/early winter so the temps were lower & there has been more idle time, so mpg will be naturally worse.

My truck is a 6.2 Denali & I think the mileage computer is averaging 15.7ish over the last several hundred miles. If I baby it or drive conservatively, I can get in the high teens or low 20’s.

 

I dont have much idle time either. Even when its cold out i only let it sit for a few minutes to get everything warmed up. With heated seats and steering wheel theirs no need to let my truck run for 10-15 minutes to get warm. Thats insane that your 6.2 is getting the same MPG as my 5.3. I'm making a trip to camp this weekend which is about 140 mile round trip and 90% highway. I will drive up stock and drive home with the 87 tune and see if theirs a difference.

[Bill Reinhardt]

My MPG's dropped when I installed the Diablo MPG tune with a Diablo TCM tune (either firm or hard shifts). Returning the TCM tune to stock fixed this. I hated the canned Diablo TCM tune anyways.

 

Did you apply a Diablo TCM tune by any chance?

Edited April 18, 2018 by Bill Reinhardt

[Clutch Bo]

i got my 5.3 2014 silverado tuned focusing on hp more than mpg and i manage to get 18.6 at best on hwy and around 12-15 city WITH 24's and 35's, true duals with no muffler, and not even a cold air or long tubes or anything.

 

POWERHOUSE PERFORMANCE in Grifton NC is the best tuner in NC

[Billy Smart]

I would say the commute you drive keeps you in the 4 cylinder mode most of the time. Tune probably disabled dod. Your average of mixed driving would be very similar without dod. Freeway driving will suffer some. The faster you drive, the less you are in dod stock. My tune hurt freeway driving by maybe 3 mpg’s immediately on the way home after tuned. But, all the terrible hesitation and off throttle problems with dod are eliminated, making it well worth it. The 6 speed trans tune can be set by gear with hptuners. Maybe a custom tune allowing dod at freeway speeds is a good solution. I have an 8 speed trans and have not played with activating dod in specific gears or speed. My tuner said my truck was his first 8 speed with e-85 that he tuned that requested dod on freeway. I have since bought my own hptuners from him and not played around. He set it for 80 km, but it never worked, I never really cared. My truck is no longer my daily.

[aseibel]

9 minutes ago, Billy Smart said:

I would say the commute you drive keeps you in the 4 cylinder mode most of the time. Tune probably disabled dod. 

I was thinking the same thing. If your tune prevents the truck from entering V4 at 60 mph, you will then lose the built-in fuel saving benefits of that system. I would check that out first and see what your AFM is doing.