Fuel mileage loss, Cummins vs Hemi

[loveracing1988]

So I have been itching to get the stock tires off of my truck since before I bought it. I can't seem to get my mind made up to pull the trigger though. My last truck was a 2014 2500 with the 6.4 and 4.44 gears that I installed 35x12.50r17 general grabber x3's on and loved those tires, for the 2000 miles I got to drive on them. I would love to go with those same tires again on my new truck but I'm concerned about fuel mileage. On that truck I had 285/75r17 open country at2's on it before the generals and when the generals were installed I lost about 1.5 to 2 mpg when I installed them. Yes I know if I wanted fuel mileage I should have bought a car. My question is will my Cummins lose as much mileage? I'm ecstatic with what I'm getting so far, my current tank is reading 18.6 with my normal driving, which is only about 6 mpg more than my hemi would be reading so like I said, ecstatic. I just don't want end up losing all of the mileage I just gained. The other tire I'm considering is the General grabber atx but I really love that red lettering...

 

[Dwilly]

My 2019 Diesel is 2L per 100km worse than before with my 37s. You'll notice it. I find myself using tow mode a lot to ease wear on the transmission.

 

[Squatch]

I don’t think you’re going to notice much of a change, 37s are a much bigger jump than 35s I’ve said it before and I will say it again, the Cummins is a honey badger and it don’t give a f***. Just remember if you don’t correct for your tire size the lie-o-meter is going to show less mpg than it would before because it thinks for every revolution of the tire the truck has gone a shorter distance.

 

[gimmie11s]

You will absolutely notice a change. On my 2016 cummins 2500 i went from the factory ~33" transforce junk to an all terrain in 35" and lost 2 mpg tank after tank confirmed by hand calc.

 

[Dwilly]

Yes mine was hand calculated as well. It actually does 1.2 km for every 1 km the speedo shows. I factor this in to my calculations.

 

[Squatch]

Maybe I never noticed on my previous trucks cause I’m not the type to hand calculate my mileage... so I’d believe those guys over me

 

[loveracing1988]

You will absolutely notice a change. On my 2016 cummins 2500 i went from the factory ~33" transforce junk to an all terrain in 35" and lost 2 mpg tank after tank confirmed by hand calc.

OK so it's about the same loss. I guess I'll find out because I ordered the same tires again and they'll be in next Tuesday.