Gas mileage after putting on bigger tires

I recently changed the tires on my truck. I went from 275/55/r20 nitto ridge grappler to a LT 285/55/r20. I have not upgraded any suspension parts. Everything is stopped. Since changing tire size my gas mileage went from an average 18-19 mpg to 13-14 mpg. Some one told me I could reprogram my transmission with tuner to get better gas mileage. Is there anything that I can try to better my situation? I should also add that the original tire that was on the truck was only a four ply tire. The new tires are 10 ply tire so there is a little bit of weight difference.

 

That tire is .4 inches bigger, thats not making a difference you're just tracking it for too short of a time or wrong

 

The original tire on the truck was a 4 ply tire and I have a 10 ply tire now. The 10 ply tires are about 10lbs heavier a piece. Would that make a difference

 

More rotational mass would, just not a big difference, you'd probably get nearly the same number if you calculated it over the same span of time. You could've even just done more start stop around town driving which would've gave you that 13-14

 

I will get some hwy time in and see the mileage. Thank u

 

Also make sure you’re calculating by hand and not what the computer is saying on the dash; PSI also matters a good bit

 

That unsprung weight makes a big difference, so I am not surprised entirely that the mpg went down. I am actually impressed with your original mpg! Lol

I went from a 275/55-20 to a 275/60-20, but I intentionally picked a lighter tire than stock. I have seen no mpg loss, but I was only getting 14.2 anyway lol

 

An extra 10 pounds of weight on each tire will have a noticeable impact on MPG’s.

And moving the larger tire from a dead stop is what is hurting you OP.

Years ago I went from a P265/65R17 AT Nitto Terra Grappler G2 to a Michelin LTX P265/70R17. This was on a 2012 Tacoma that was used mostly on the highway as it was the family car. The Michelin’s were about 4 pounds lighter.

Because it was a 2012 I had to hand calculate the MPG’s and make the adjustments for the larger tire size.

The Michelin’s never beat the Nitto’s. I believe getting a larger tires increases the energy necessary to start from a dead stop IF the tire weights are not significantly different. Weight and torque required to move are not friends of MPG’s.

I am currently testing the same thing on my Tundra.

Factory TRD OR rims: 31
Michelin AT’s P275/65R18: 41
Combined: 72

FN Five Star rims: 24
Nitto Terra Grappler G3
285/70R17: 48
Combined: 72

I have zero expectations that I will not LOSE MPG’s but I absolutely love the setup. It’s a hair firmer ride but much more supportive in the turns (highway and town speeds…). I ultimately choose this to get the height without drastically changing factory weights (unsprung) around. I have done that in the past and have regretted it.

 

Tuning won’t gain you much more efficiency, but it will operate better. The torque increase from a regular fuel tune with transmission adjustment could get an an extra 1-2 mpg at best. The 5.7L motor doesn’t see the efficiency gains as much as the 6 cylinders do. Either way, a performance tune will be an excellent choice.

 

Supposing identical tires. Let’s say Michelin ltx ms. Same size. Same tread. Only difference is one is 10lbs more. What is a noticeable mpg difference?

 

From 17 (highway according to Toyota) to 16 MPG’s is just under a 6% loss. That’s noticeable…

 

That helps me understand. When you say according to Toyota do you mean the dash mpg?

 

What the window sticker says. And unfortunately with city driving that percentage goes up because it’s less efficient. Many forum members don’t get anywhere near 17. In all honesty as minor as it is, larger tires or heavier tires than stock will have a financial impact. Just something to ponder before jumping in…

 

Welcome to the club OP! Did your salesman not inform you that you were also buying a gas station when you purchased your truck? Yeah, mine neither, but life is too GD short to sweat it. Just adapt and accept low MPGs is better than repairs

 

I just looked at my window sticker. I have a 2023 4x4 Crewmax limited. City is 17 highway is 22. I do get 21 highway if I’m doing 65 and on level ground. Obviously drops if I go faster or start climbing in elevation. Guess I’m doing better than most. I’m happy.

My 3.5 ecoboost did about the same on mpg.

 

I have the 5.7 V8, but nonetheless I would assume size and weight would have a similar impact to a turbo as it would to a non turbocharged motor. I honestly don’t see how it would not.