Newer Tires, Poor gas mileage, what is main cause?

I recently got new 17 inch wheels and goodyear wrangler all terrain tires that have a pretty aggressive knobby tread pattern. These replaced the stock 16 inch and more road style tires on my TRD Off-Road. With the new tires the best mileage I can get is about 18-19 mpg at 65 on the highway compared to about 22 with the stock tires and rims.

Question is, is the culprit for the loss in economy more due to the larger diameter of the wheels? Or the knobbiness of the tires and road friction?

 

I'm thinking the new tires are heavier than your original tires. See if you can find the weight of the new tires and compare.

 

Your milage loss has to due with rotational mass and wind resistance. If you went with a larger tire more weight. If you went with a higher load rating more weight. If you tire is significantly wider more wind resistance. So you take a hit on milage.

 

Cool, thanks for the input gentlemen!

 

An aggressive tread pattern has a higher rolling resistance. Heavier tires = more energy required to get the tires rolling. Those two will reduce your efficiency and reduce mpg.

 

So would you say its more that I have a heavier tire causing this and less the fact that wheels are an inch in diameter bigger? Like if I went back to less aggressive pattern and more to a highway tire i might recover a little of that mileage?

 

When I got my 2020, I was getting 25.5mpg. I installed some heavy 10 ply's and I now get 21.5mpg.

 

Did you get your speedometer adjusted for the larger tires?

If not you will need to increase your mileage by a %.

 

I had the dealership do it, so I would think they would have, but I'm not sure.

 

18-19 still seems pretty bad for just upgrading the tires. I have a 3 in lift, e rated tires (33s) and about 400lbs of armor and after market things tacked on, and get 17-18mpg consistently. Did they replace the fuel pump too? I did notice a slight drop when I had the recall done

 

Definitely check as it will have an impact. Just for reference you're now running a larger circumference tire. In my case I went from 245/75R16 to 275/70R17. Knowing this I multiply my mileage by 5.6% (I didn't get the speedo reset). I also know that I'm above the speed limit if my speedo is the same as the posted limit by 5%.

What others have mentioned that I didn't above is that my new tires are also heavier which will impact mileage as well. With my lift and taller/heavier/wider tires I took a pretty decent hit to my MPG.

Anytime you go taller/wider/heavier/more aggressive tread you're impacting unsprung weight, rolling resistance, circumference, etc. which will impact MPG.

 

Is that recall for 2021 model year as well? If so I don't know that it was done.

 

Thanks this is super helpful.

I went from 265/70/16 to 265/70/17, so not a huge jump and according to the this is only about a 3-4% difference in turn rotations.

 

You have to compare the actual weights, otherwise we're just speculating. And wheel size may not matter in your case. If you went from 265/70R16 to 265/65/17 (stock OR and sport tire sizes, respectively) tire diameter, width, and revs/mile are basically identical.

 

Combo of everything talked about so far. Bigger tires/wheels & heavier/tread pattern will all make a difference. I’d bet your mileage isn’t as bad as your cpu says it is. Hypertech and Rough Country make speedo calibration kits, which are the only ways to make it accurate. Unless the dealer installed one of these, the speedo/odometer is off

 

Not sure. I know it effects at least 2016-2019. I would hope since they've now known about the issue for a few years it would be correct from the factory for the 2020+.

 

Let's do some math, but first of all you will never average 22 mpg. The best you will ever do is around 20 mpg so let's start there.
Your tires are going to cost you about 5% in efficiency, or 1 mpg.
Lets say you drive 15K miles a year and gas is $3.00 a gallon:
If you got 20 mpg, you will spend $2,250 dollars on gas.
If you get 19 mpg, you will spend $2,368 dollars on gas. That's $118 a year.

If tires cost $800, It will take you almost SEVEN years to recover your money for one mpg increase.

Sometimes it pays to put it in perspective.

 

Is this a real question???

 

It's a Friday but the OP truly seems genuine to learn.

 

I think so, which is why I took a minute to answer his question fully.