285/65R20 Nitto Ridge Grapplers on a Powerboost... recalibrate?

[JediNut]

Hi Folks,

When I bought my truck, I had the dealer level it and throw some 285/65R20 Nitto Ridge Grapplers on there. As I see everyone else's great gas mileage from their PBs, even with larger tires on them, I am wondering if maybe the dealer didn't update the computer with the new size of my tires.

Part of me says that wouldn't make up for the huge difference in gas mileage (I am getting only about 17-18 mpg according to the truck). I know that I could use Forscan to check the setting, but I am a Mac guy and Forscan doesn't work on a Mac (or even in a Windows Virtual Machine ON a Mac).

I know that the level and bigger tires are going to have a negative impact on gas mileage overall, but I guess that I am asking if anyone has any idea what kind of impact it makes on the MPG calculations on the truck if the size setting isn't adjusted.

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[Hebed118]

Curious what others think on this as well.

About a 20lb increase in tire weight alone is pretty huge though. I wouldn't think its far off actual.

 

[Oxford_Powerboost]

You might be a few % higher on mpg than it says you are. But honestly, that’s about the mileage I expect once I level mine and put heavy tires on. Makes a huge difference

 

[chill_will]

Pre level and 295/60s I was getting 24+. After I’m still getting 20+. Shorter trips in town I’m getting 21-22. I did have my Speedo calibrated in forscan

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