Could tire size difference be killing my MPG?

Joined
Jun 24, 2005
Messages
703
Location
Omaha, Nebraska
 
On the wife's 00' 4Runner, I just swapped out the worn 265/70R16 Goodyear Wrangler ATs for a set of 265/75R16 Kumho AT825s. Last fill up, the wife calculated the mileage at 16.5MPG. We had been getting 19 pretty regularly.

I think she is doing the math wrong, or she didnt reset the odo. But do you guys think I would lose 2.5 MPG going from a 265/70 to a 265/75?

Hodag
 

bkg

Joined
Oct 1, 2004
Messages
657
 
hodag said:
On the wife's 00' 4Runner, I just swapped out the worn 265/70R16 Goodyear Wrangler ATs for a set of 265/75R16 Kumho AT825s. Last fill up, the wife calculated the mileage at 16.5MPG. We had been getting 19 pretty regularly.

I think she is doing the math wrong, or she didnt reset the odo. But do you guys think I would lose 2.5 MPG going from a 265/70 to a 265/75?

Hodag

First of all, the 75s are about 4% larger in circumfrence than the 70's, at least according to the PD of my 4runner. So you need to multiply the 16.5 * 1.04 to get your actual mileage. Bigger tires do affect mileage, though, aside from speedo differences. That said, my 96 gets 19.25 (corrected) cruising at 75-80 w/ 75s, but it's not stock, either.
 
Joined
Jun 24, 2005
Messages
703
Location
Omaha, Nebraska
 
Thanks for the info. My wife is an engineer, so doing some extra math is right up her alley. After I posted, I remembered that I worked on the battery cable between fill ups, so that also may have affected the total mileage.

Thanks for the help, Hodag
 

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