MPG with wrong tires - Lessons learnt

mj78inds

Hi,
I have been trying to find some posts on how MPG is impacted when the right tire specs are not followed, I learnt the hard way. Here it goes - I have a 2012 Toyota Camry LE, as my car neared 60k miles (~2015), we went in for tire changes. The local Disc***t Tire store (Schaumburg, IL) did not carry 205/60R/16 tires which are recommended for my car. They conveniently recommended 215/60R/16 which they had in stock, they assured me it is not a big deal (it would not impact performance, mpg etc.). Well, when I replaced my tires again (~2018), I realized it is a BIG DEAL, as explained below:
1. With the 215/60R/16 - my car averaged 25.5 mpg (lowest grade fuel out of the three options at US pumps - I guess called "regular"). I drove for 40,000 miles which is 40,000/25.5 = 1568.62 gallons of gas. With the right spec tires - 205/60R/16 - I am getting 29 mpg, which would have led to 40,000/29 = 1379.31 gallons of gas. Assuming gas was on average $2.65 per gallon between 2015 and 2018, this has led to a loss of (1568.62 - 1379.31)*$2.65 = $501.7!! (note all mpg are for highway).
2. The tires wore out in 40k miles (warranty was 60k)
23 The odometer was off by 2 mph for example it showed 72 mph when I was doing 70 (this was pointed out to me by Dis****t Tire after installing the tires!)

Thus lesson learnt! And the thing is that the specs for the tires are written on the door frame!! I should have paid attention.

Hope this was useful.

MJ

kyfdx

I agree with your premise, that you should always use the correct size, and different sizes from stock could be detrimental to fuel mileage and vehicle operation in general.

But, it's more likely that your mileage was affected by the type of tire (higher rolling resistance) than the size.

Also, since the circumference was about 4.9% larger on the bigger size, your odometer and speedometer would have been off by that much, as well. So, you actually traveled closer to 42,000 miles, instead of 40,000. That would increase your actual average to about 26.75 mpg. Still a significant drop. But, your car also has 40K miles more wear/tear than on the last set of tires.
This drops your extra gasoline expenditure to about $308.

But, your points are all valid.

I change tires twice per year (winter vs. summer), so I can really see the difference between the types of tires on the vehicle, even in the same size. This year, I switched to a new winter tire, with a more aggressive tread design, and I can already see a drop in my mileage, even though they are the same size as last year. (noisier, too!)

Thanks for your report!

mj78inds

@ktfdx
Very insightful! Thanks!