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lift and 34" tires cost me about 5-6 mpg

Augiedoggy

Active Member
Aug 18, 2021
138
36
Truck Year
2015
I seen the general consensus has been on here that 35" tires hurt gas mileage which is obvious, but I went from a lowered truck with 30" terra grappers to lifting that truck effectively 5" in the front and 7" in the back with the tire increase (5100 kit with 2" lift springs in the rear giving the truck a 2-3" lift over stock) and used 295/70/18 mickey thompson baja MTZ tires. The tire size has been entered into the computer via alpha obd and speedpo is correct. I havent done extensive highway driving but my general MPG has gone from flutuating between 22 and 24mpg to between 16 and 17. even with 3.92 gears the trans downshifts more often and now often takes fluttering the pedal to upshift compared to before. I am actually thinking of going to 33" tires dispite the 34s looking so much better on the truck I also have been looking at more conservative tread and lighter tires in hopes that there might be a set of 33.5 or larger all terrains out there that might help regain some of the trucks driving manners.

As far as how the suspension upgrades went the 5100s ride much better than what I had when I bought the truck used a couple months ago.
 

Augiedoggy

Active Member
Aug 18, 2021
138
36
Truck Year
2015
Still waiting on 34" nitto G2s that I ordered from jegs... they are not 10 ply so will save me about 20lbs per tire in weight over what I have now and hopefuly I will regain som e of the performance I had before with the 31" 4ply nitto G2s the truck came with. They rode a 100 times smoother than what I have now. I'm averaging 20mpg per tank now and the truck is very lazy in upshifting compared to before requiring a lot of feathering of the gas pedel. I do understand theres no free lunch and taller tires will change my gearing but I wasnt expecting to go from 34 to 23mpg on the highway.
 

Augiedoggy

Active Member
Aug 18, 2021
138
36
Truck Year
2015
My tires are expected to ship in the next day or 2!! ... only took four months.
In the mean time my overall mileage have dropped to 15.9mpg some of this has to be the winter blend. hopefully I see an increase with the new tires or I will be going to smaller tires as this kind of mileage hit is just dumb for looks.
 

Augiedoggy

Active Member
Aug 18, 2021
138
36
Truck Year
2015
So ironically the new 34" 4ply Nitto G2s arrived yesterday and I just got them mounted. Theres a huge difference in ride quality and the mileage is better, it's still too early to get actual figures on how much the mileage has been effected but I have noticed the truck holds higher gears a bit better without downshifting as much.
 

EcoDiesel USA

New Member
Jan 15, 2022
22
2
Truck Year
2016
Proper tuning with delete can get that back, I have one customer with 9" of lift and 37s averaging 22 in california.
 

Augiedoggy

Active Member
Aug 18, 2021
138
36
Truck Year
2015
Proper tuning with delete can get that back, I have one customer with 9" of lift and 37s averaging 22 in california.
truck is tuned with a delete now... also have straight piped and a banks intake installed.. For this reason, If I ever replace the "tuning" it will be with one I have control over options with an interface like most of the other diesels have been using for years.

If I did a lot of highway driving I have no doubt I could get the mpg average to 22 but most of my driving is in the city. Right now I havent done any real highway driving since I got the new tires but if I had to guess im optimistic for around 26mpg on the highway which is still a big hit from the 34 I got before.. The more I think about it im sure the lowering had a huge impact on wind resistance in addition to the smaller tires and its effect on the transmission gearing/ load.
EDIT in the few miles ive driven since the new tires were installed, (truck is a secondary vehicle) my overall mileage has only gone from 15.9 to 16.2 but climbing..

Dont take this the wrong way but I'm sure that 22mpg with 9" of lift and 37" comes with other criteria not mentioned like 4.56 gear change or downhill with the wind at your back... or maybe thats a singlecab 2wd truck... Theres only so much you can do with software to overcome negative gearing changes.
 
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