Gas mileage with bigger tires

DTOMKIDD · November 15, 2016

I currently have the stock 255/75/17 tires on my 2015 GMC Sierra with a 5.3 and am seeing about an average of 20 MPG. I want to up my tire size to 285/70/17 Toyo Open Country AT2's and was wondering how bad they would hurt my mileage?

JRL1164 · November 15, 2016

I lost 1 mpg city and 2 highway going to 33" KO2 with the speedometer recalculated. I get 17 city and 20-21 highway now and that's with 2" level and an add a leaf.

Andy Seibel · November 15, 2016

no simple answer. I'd guess mileage will go down maybe 2 mpg depending on a lot of factors including your driving habits. Those tires are wider, but not taller. So you may be on the lower end of mileage loss.

StretchASU · November 15, 2016

Stock was 18 city 20.5 highway averages

Leveled, bottom of air dam removed and 295/70/17 Toyo RT's and its 16.5 city and 18.5 highway averages. Hand calc'd.

DTOMKIDD · November 15, 2016

Thanks for the response everyone. That makes me feel alot better, I was under the impression my gas mileage was going to suffer a lot. Now I'm even more excited to buy these tires!

tyrich88 · November 16, 2016

I have 275/70/18 BFG KO2's and still get 17-19 highway (unless the west texas winds are blowing like crazy)

they are a little taller than what you're looking at but only by about 0.25"

I also have a level, and camper shell

My in town mileage suffered the most because these are 10 ply tires, so they're heavy.

Donstar · November 16, 2016

I currently have the stock 255/75/17 tires on my 2015 GMC Sierra with a 5.3 and am seeing about an average of 20 MPG. I want to up my tire size to 285/70/17 Toyo Open Country AT2's and was wondering how bad they would hurt my mileage?

Are you sure you have 255/75r 17 and not 255/70r 17? If you do have the "75" I'd appreciate seeing a picture. I ruled out the 285's because of the weight increase but am interested in the higher tire size with an aspect ratio of 75.

DTOMKIDD · November 16, 2016

Are you sure you have 255/75r 17 and not 255/70r 17? If you do have the "75" I'd appreciate seeing a picture. I ruled out the 285's because of the weight increase but am interested in the higher tire size with an aspect ratio of 75.

I could be mistaken, but I'll go out and check on my lunch to make sure and grab some pictures if they are the 75's.

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tyrich88 · November 16, 2016

Are you sure you have 255/75r 17 and not 255/70r 17? If you do have the "75" I'd appreciate seeing a picture. I ruled out the 285's because of the weight increase but am interested in the higher tire size with an aspect ratio of 75.

If you are worried about 285/70/17s because of weight. Nitto and toyo both make a version of their all terrain tire that is not 10 ply. So the weight increase is VERY small with the 4 ply tires in that size.

I wouldn't take them offroading in very crazy situations since they're thin. But for highway driving they would be great and not hit your MPG too much at all.

Donstar · November 16, 2016

If you are worried about 285/70/17s because of weight. Nitto and toyo both make a version of their all terrain tire that is not 10 ply. So the weight increase is VERY small with the 4 ply tires in that size.

I wouldn't take them offroading in very crazy situations since they're thin. But for highway driving they would be great and not hit your MPG too much at all.

Thanks for the suggestion!

DTOMKIDD · November 16, 2016

Are you sure you have 255/75r 17 and not 255/70r 17? If you do have the "75" I'd appreciate seeing a picture. I ruled out the 285's because of the weight increase but am interested in the higher tire size with an aspect ratio of 75.

I was mistaken They are the 255/70r 17's. Not sure where I got the the 75 from haha.

Donstar · November 16, 2016

I was mistaken They are the 255/70r 17's. Not sure where I got the the 75 from haha.

Thank you for taking a look. The diameter of the "75" is 1" larger than the "70" which is significant. I've been trying to get a picture as I would be stuck with the look for a long time! Good luck with your tires. Your 285/70r 17 replacement tires will be 1.6" taller than your stock tires. I suspect you'll notice more of a mpg loss in city than highway driving.

quail hound · November 17, 2016

RCSB, leveled, 285/70/17 bfg ko2s, fully loaded with gear for two guys and three dogs. Here are two recent trips I took, the Speedo isn't recalibrated so I actually did a little better than what's shown.

Best tank was 22 mpg on clear premium.

Sean D · November 18, 2016

35's getting 13.0 MPG

DTOMKIDD · November 18, 2016

Thank you for taking a look. The diameter of the "75" is 1" larger than the "70" which is significant. I've been trying to get a picture as I would be stuck with the look for a long time! Good luck with your tires. Your 285/70r 17 replacement tires will be 1.6" taller than your stock tires. I suspect you'll notice more of a mpg loss in city than highway driving.

No problem!

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RCSB, leveled, 285/70/17 bfg ko2s, fully loaded with gear for two guys and three dogs. Here are two recent trips I took, the Speedo isn't recalibrated so I actually did a little better than what's shown.

Best tank was 22 mpg on clear premium.

Thanks for sharing your results, that makes me feel a lot better about going that size in tires.

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