Fuel Mileage Questions

dyland96 · May 7, 2025

First off hello all this is my first post on this page. Second, I am thinking about replacing my factory 275/60R20 with a slightly larger 275/65R20 tire and am curious if anyone has done the same thing and how it changed (if any) the fuel mileage. To my u see standing it’s only about a 1” difference in size and the tires I will be using are only 7lbs heavier per tire. Also if anyone has any insight on the best way to level the truck please drop that information below as well. I have heard the CVs and ball joints aren’t in a good angle with regular leveling kits like those used on non AT4 trucks. Thanks

Andystoy AT4 · May 7, 2025

Well if I remember correctly, way back, 7 lbs. of rotating mass per tire(equals to one HP) will equal to an increase of about 4 HP that the engine will have to produce at cruise. The increase in height will reduce your final gear ratio slightly. The final result may not be a big drop in fuel mileage but I would expect at slight reduction in a perfect scenario. JMO

gemarsh · May 7, 2025

Welcome.

Thunder_Grey2025 · May 7, 2025

I'm running 275/65's and I dropped about 1mpg that I can notice. I did get one of the lightest tires they offered though. I think it's 47lbs, I'd have to check. It's the Nitto Terra Grappler G3's in the SL version not the E rated.

Civ_Eng · May 12, 2025

dyland96 said:
First off hello all this is my first post on this page. Second, I am thinking about replacing my factory 275/60R20 with a slightly larger 275/65R20 tire and am curious if anyone has done the same thing and how it changed (if any) the fuel mileage. To my u see standing it’s only about a 1” difference in size and the tires I will be using are only 7lbs heavier per tire. Also if anyone has any insight on the best way to level the truck please drop that information below as well. I have heard the CVs and ball joints aren’t in a good angle with regular leveling kits like those used on non AT4 trucks. Thanks

To give you an idea, I went up in size to 34s that are load E rated and weigh approx. 20 lbs more per tire than the stock tires. Prior to the tire change I was seeing 30+ mpg at 60-65 cruising speeds on highway. Now I’m around 25-26 at that same speed. I changed the tires at about 500 miles on the odometer and over the past 7,000 miles, I’m averaging 23 mpg with a mix of 20/80% city to highway driving. I would expect you to not take as large a hit to the mpg.

mandalorian · May 14, 2025

running wildpeak AT3 34" tires as well with a 2" leveling kit. round trip driving from VA to FL (12Hr one way driving) i was getting on AVG 25mpg this past week only needing to stop once for fuel midway through the drive. take it for what it is...everyone drives different. either way, you probably won't notice any noticeable difference with that tire selection, especially if its a highway tire vs an AT. good luck with your decision and welcome to the forum!

muddernuker · Jun 1, 2026

Just finished a trip from Tucson to our home in NM. Total distance of 452 miles and averaged 27.2 MPG hand calculated. Currently running 295/60R20 KO2s (34”). Average speed of 70 MPH. Most highway was doing 78-80MPH. Can’t complain.

pinebaron · Jun 2, 2026

Welcome

Don't forget tire pressures will also impact mileage.

muddernuker · Jun 2, 2026

pinebaron said:
Welcome

Don't forget tire pressures will also impact mileage.

I have them at the recommended specs.

RebelDS · Wednesday at 7:18 AM

Tire recommended specs that’s on the vehicle is useless. Tire types are different. A KO3 in LT sizes has 65 PSI max. A Toyo Open Country A/T III has a 44 PSI max and the tires I’m running have a 51 PSI max. So I’m running 42-44 for highway driving (off-road would be a lot lower) for my tires. That would be way too much for Toyo and not enough for KO3. This is for highway driving to get the best mileage

If you go by the recommended PSI shown on the truck, you’ll wear the tires out a lot faster and get more wear on the outer edges and less in the middle because they are under-inflated. I’ve never understood why the vehicle puts those numbers on there. It’s actually the minimum safe PSI, not the PSI that you should be using