Will 38's kill my gas milage?

[vst]

Like the title says will moving from a 37x12.50x17 to a 38x13.50x17 kill my milage. I currently average about 17 mpg on my 37's with 5.13 gears. I currently run the Yokohama geolander x-at and thinking of maybe switching to the Patagonias XT's they are only about 3lbs heavier than my current tires.

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[sharpsicle]

Bigger and heavier tires will always have a negative effect on your mileage.

How much of a change do you consider “killing” your mileage to be?

 

[Escape.idiocracy]

Keep us posted.
Really happy with the XT’s so far. Recent snow was a test…. lol did great!

I regret not just ordering 38’s right out of the gate….

 

[Weldit]

I can’t imagine another inch and 3# making more than 1mpg difference in fuel mileage. And brand to brand they vary so much…. are the current tires actually 37” and new tires actually 38”?
Hell I’m only averaging 17mpg with 34” tires.

 

[vst]

I can’t imagine another inch and 3# making more than 1mpg difference in fuel mileage. And brand to brand they vary so much…. are the current tires actually 37” and new tires actually 38”?
Hell I’m only averaging 17mpg with 34” tires.

yeah im thinking more the 13.5 wide vs the 12.5 would potentially make more of a difference. My commute is about 30 miles to work one way but the road I take I don't really go above 60 mph and I have a GFC camper and im still able to average 17 I've even seen 18 mpg with my current 37's.

 

[antwon412]

Yes. Thread can be closed now.

 

[KEG2021]

Maybe nitrogen fill would help???

 

[TheRealStreetcommander]

Lest we forget, they reduce mileage immediately… but very slowly, they kill your bearings, ball joints, steering systems, driveline, shocks and bushings, wear out your brakes more rapidly, increase stopping distances, decrease acceleration, may be illegal in some states, and yes, likely contribute to the death wobble enigma.

It’s a Jeep thing.

 

[Russ2023]

Anytime you add more unsprung weight it’s going to affect gas mileage. It may be negligible but I’ve never seen an example of where more weight equaled better mpg. Is there a practical reason for wanting to go up one pant size or is it all about aesthetics? If the latter is the case remember that such a minimal increase in size is hardly going to be noticeable so I wouldn’t do it for bragging rights or anything. Not much to gain IMO.

 

[Escape.idiocracy]

Maybe nitrogen fill would help???

?? wonder what bottle swapping a nitrogen bottle goes for? ? co2 isn’t $20 buck!

 

[NHyde]

All the answers here are false. Everyone knows the bigger the tire the better the MPG.

 

[bleda2002]

It's an inch and 3 lbs, you won't notice it considering it's already killed from 37s. I went 37s to 39s back to 37s and now 38s and mpg was all within .5 of each other

 

[Jt_gladi]

Not by much more, a 38 is about a 2lb difference from a 37 (depending on tire)

when I was looking for my set the rep pulled up specs on my tire (nitto Tera grappler) and it was about a 2lb difference per tire from 37 to 38

 

[gladtohave]

If your rolling 37's you've already taken the big MPG hit so the 38's are not going to "KILL" your current mileage but might shave a MPG off .

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