3.0 DURAMAX Tire size and MPG

[R.C.]

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]

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. 

[paxamus]

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. 

[SC4R3C120W]

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.

[newdude]

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.  

[R.C.]

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.]

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.]

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

[R.C.]

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 

[acmech87]

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?

[Obone]

I lost 4-5 mpg with mud tires