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3.0 DURAMAX Tire size and MPG

R.C.

By R.C.
in Modifications, Wheels & Tires

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R.C. Enthusiast

R.C.

Posted
Posted

I’m new to the forum so apologies as this has probably been discussed. If so could you direct me to that post?

 

I have a 2021 - 3.0 Duramax 4x4 with factory, 265/65R18 tires. It’s getting time for new tires. I’m considering a one size up, 275/65R18. Has anyone done this and had a significant decrease in MPG’s? (Also with a leveling Kit?) Any issues with tire scrubbing at full turn?

I enjoy having a full size truck that does get good fuel mileage and don’t want to adversely effect it. 
Thanks

 

ToothDoctor New Member

ToothDoctor

Posted
Posted

I think you could go up a size without any noticeable difference. I have a '21 Trail Boss. The factory tire size is the same as yours. Granted, the Trail Boss has a factory 2" lift, but I was able to go up to 295 70 18 Falken Wildpeaks with the stock suspension.  My speedometer is 2 mph too slow with the new tires and gas mileage has remained the same. 

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paxamus Enthusiast

paxamus

Posted
Posted

I have a 21 1500 with the 3.0L Duramax as well.  I installed a 3"Cognito coilover in the front and 1"block in the rear and have 35x11.5 on the stock 20"wheels.  I noticed a decrease in my MPG with my best pre lift being around 28 and best now is like 25 (i drive a lot and mostly see 23- but I do drive 80!)  I also took off the front air damn so there is a decrease in aerodynamics as well.  I recalibrated my speedometer with the Rough Country speedometer calibrator as well so the numbers are fairly accurate. 

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SC4R3C120W Enthusiast

SC4R3C120W

Posted
Posted

I have a 20 RST in 2wd. I used to average 29-33mpgs with the 265/65. I then added the Rough Country 2.5" lift and put 275/70/18 tires on my stock rims. I've driven about 15,000 miles with them and my average is now 27-29mpg. I noticed that the weight was the biggest contributor to the mileage, as well as speed. When i went to buy my tires (bridgestone dueler a/t revo3), i chose them because they were one of the lightest and quietest, but still had an off-road look.

 

If i keep my speed down from 70 and lower, i'll get good mileage (back to low 30's). Anything of 70 now and it drops to 26-28.

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newdude Senior Enthusiast

newdude

Posted
Posted
On 10/16/2022 at 10:41 AM, R.C. said:

I’m new to the forum so apologies as this has probably been discussed. If so could you direct me to that post?

 

I have a 2021 - 3.0 Duramax 4x4 with factory, 265/65R18 tires. It’s getting time for new tires. I’m considering a one size up, 275/65R18. Has anyone done this and had a significant decrease in MPG’s? (Also with a leveling Kit?) Any issues with tire scrubbing at full turn?

I enjoy having a full size truck that does get good fuel mileage and don’t want to adversely effect it. 
Thanks

 

 

 

That size is a factory size on the Diesel Off Road Pkg that's available, and the 20s are a 33 inch tire so you won't have any rubbing concerns on anything up front.  

 

As for MPG hit, a couple factors.  The tread you pick can change it (highway vs. AT vs. MT), the added weight results in more rotational mass too.  

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R.C. Enthusiast

R.C.

Posted
  • Author
Posted
On 10/16/2022 at 1:09 PM, ToothDoctor said:

I think you could go up a size without any noticeable difference. I have a '21 Trail Boss. The factory tire size is the same as yours. Granted, the Trail Boss has a factory 2" lift, but I was able to go up to 295 70 18 Falken Wildpeaks with the stock suspension.  My speedometer is 2 mph too slow with the new tires and gas mileage has remained the same. 

Thanks for the response 

R.C. Enthusiast

R.C.

Posted
  • Author
Posted
5 hours ago, newdude said:

 

 

That size is a factory size on the Diesel Off Road Pkg that's available, and the 20s are a 33 inch tire so you won't have any rubbing concerns on anything up front.  

 

As for MPG hit, a couple factors.  The tread you pick can change it (highway vs. AT vs. MT), the added weight results in more rotational mass too.  

Thank you for the response 

R.C. Enthusiast

R.C.

Posted
  • Author
Posted
5 hours ago, SC4R3C120W said:

I have a 20 RST in 2wd. I used to average 29-33mpgs with the 265/65. I then added the Rough Country 2.5" lift and put 275/70/18 tires on my stock rims. I've driven about 15,000 miles with them and my average is now 27-29mpg. I noticed that the weight was the biggest contributor to the mileage, as well as speed. When i went to buy my tires (bridgestone dueler a/t revo3), i chose them because they were one of the lightest and quietest, but still had an off-road look.

 

If i keep my speed down from 70 and lower, i'll get good mileage (back to low 30's). Anything of 70 now and it drops to 26-28.

Thanks

  • 3 weeks later...
R.C. Enthusiast

R.C.

Posted
  • Author
Posted
On 10/24/2022 at 1:34 PM, SC4R3C120W said:

I have a 20 RST in 2wd. I used to average 29-33mpgs with the 265/65. I then added the Rough Country 2.5" lift and put 275/70/18 tires on my stock rims. I've driven about 15,000 miles with them and my average is now 27-29mpg. I noticed that the weight was the biggest contributor to the mileage, as well as speed. When i went to buy my tires (bridgestone dueler a/t revo3), i chose them because they were one of the lightest and quietest, but still had an off-road look.

 

If i keep my speed down from 70 and lower, i'll get good mileage (back to low 30's). Anything of 70 now and it drops to 26-28.

Thanks 

  • 6 months later...
acmech87 Enthusiast

acmech87

Posted
Posted

Sounds like I might have an issue or something. My RST is stock with the babymax and the best ive seen is 25.

 

Are y'all using the 25/50/400 mpg calculator in the dash options or doing a manual old school math calculation?

  • 5 months later...

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