MIleage of 20" tires vs 18" tire

The standard for most editions of 2025 Tundras is 18" tires. There are options that upgrade the 18" to a 20" tire.

Now in 10,000 revolutions 20" tires will travel 9.9116 miles. The 18" tires, in same number of revolutions, travels 8.917 miles. So a 20" tire travels 1.1x farther than a 18". That affects mileage and MPG.

The question is does Toyota set the computer to calculate mileage and MPG based on 18" tires or 20" tires? If it's based on the 18" tires and you have 20" tires like me, then the actual mileage and MPG is about 1.1 times what the car says.......If the car reads MPG of 15.5 MPG, you are actually getting about 17 MPG. Anyone know the answer to this math question????

While I'm at it, here's another math question....my Tundra says I am down near 1/8-1/16 of a tank left and the computer says I have 32 miles left. At the 16 MPG I am averaging, thats 2 gal left. When I fill up, I can only put 24 gal in. So with the 2 gal, I have accounted for 26 gal. The stats say the Tundra has a 32 gal tank which makes it a 6 gal reserve. That seems really high to me. Where has the disappearing gas gone....is 6 gal reserve legit?

 

Toyota does not put 18” or 20” tires on anything. It uses 18, 20 or 22 inch wheels to mount tires of incredibly similar diameter on. The calibration for the Speedo will work for any of the available wheel and tire combos.

 

6 gallon reserve is correct.

 

If this is a real post, you need to calculate overal TIRE size. Not WHEEL size. No one is riding around on their 18” and 20” wheels straight on cement. Well, unless you catch some fun high speed pursuits they might get down to riding on their wheels. Enjoy.

 

is the circumference of a 18" wheel/tire different from the circumference of a 20" wheel/tire?
DRP does that mean that after the gas gauge hits E I still have 15mpg x 6g=90miles left???

 

Hey OP,

That will depend on the tire and wheel combination.

For example, my stock tires and wheels are 265/60/R20. The diameter in total would be 32.5" and to cover a mile, it'll do 620 rotations.

But if I switched to 18" wheels with 265/70/R18 tires, I'd get nearly identical results. Diameter is 32.6" and would need 619 rotations to cover a mile.

 

Jigenax thank you for taking the time to provide the very helpful information. Is seems like the 18" wheel is smaller than the 20" but the 20" tire is smaller than the 18" so the net result is they both have roughly the same circumference. NUTS I was hoping the calculations from my first post were correct so that when it says I'm averaging 15.9 MPG, i ws really averaging over 17mpg. Now I have to figure out why I'm getting such poor MPG. I should be getting 18 overall but I'm getting less than 16.

 

There's lots of different reasons for poor gas mileage. Poor quality fuel, underinflated tires, clogged air filters, dirty spark plugs, driving modes (Sport/Normal/Eco), towing a trailer, driving in city or highway, hilly/mountainous or flat lands, etc. Good luck finding the cause and correcting it.

 

Why should you be getting 18 overall?

 

As stated previously, there are many factors that will affect mileage; the biggest being your right foot.

Since you have a '25 it's likely a safe assumption you have very few miles on it.
It is VERY common for mileage to improve on these trucks all the way to 10K miles. Mine was done increasing by roughly 6K miles.
My mileage when new was very similar to yours; 15 to 16 average, and 18 was not uncommon after I had put some miles on it.

Then I went and put bigger tires on it and leveled it and mileage dropped noticeably, and predictably. (But that's an entirely different discussion.)
I'm sure someone else will say it, so I might as well....
Don't forget you bought a truck, not a Prius. Gas mileage is not the normal realm of 6000 pound vehicles with the aero of a brick.

 

That's what the math says. Not sure i care to test it too far though. Also, leaving gas in the tank helps keep the fuel pump cool.

 

Jigenax 2025 Tundra Limited, no cover on bed yet, 1990 miles (evenly divided between city and hwy). Everything is clean and up to date. I'll wait until I get the bed cover on and have 10,000 miles on the truck

KNABORES When I was researching new trucks, I based what my MPG on my old truck, a 2018 Tacoma. They advertised 22/18/19 and I got 20/16/17-18 on the Taco so I figured my Tundra listed at the same EPA of 22/17/19 so I figured I would get 20/16/17-18

At least it's better than my 2004 Tundra.....I got 15-16/13/14

 

My wife's Lexus, when she drives it averages 32mpg. When I drive it I seldom can get 19-20mpg, usually less. Just saing