
Originally Posted by
El Chupacabra
It's just one factor.
Are you basing your observed MPG on a dashboard readout of MPG? Or based on hand calculated driven miles + actual fuel consumed?
I hand calculate almost every tank.

Originally Posted by
summit
Assuming both tires are equally worn, and that the actual tire size matches the dimension, which they often don't, the size difference accounts for a 3.4% mpg difference in favor of the Blizzak because of differences in the indicated mile traveled vs true.
The BFGs are 5# heavier per tire than the Blizzaks (assuming a DMV2). That would have minimal effect I think. Wheels can easily 10# different between alloy wheels... and steel vs a lightweight alloy even bigger difference.
You gave 14 vs 16 mpg, a 13% difference... now I think probably you need to re-measure that and calculate to 3 significant digits. Because 14.4 vs 15.5 (largely explained by size and weight) is way different than 13.5 vs 16.4 (explained by the factors Jong listed)!
Thanks for the info. I think the wheels are the same, the BFGs came with the car and I believe were just OEM wheels, and the second set was purchased from a guy with a similar Sequoia, so also OEM.
The BFGs are more worn, about 50% tread while the Blizzaks are close to new. But that difference would make the MPG difference less not more (ie the BFGs are now closer in size to the Blizzaks).
It's not easy to more precisely calculate for a couple of reasons. One, every tank is different, with a different mix of miles and driving conditions. And two, I didn't notice this until I put the Blizzaks on, so I did not have the opportunity to try and create a "control tank". There is no question a noticeable difference, way more than 3%, but beyond that it is hard to be precise. Maybe in April, before I switch back, I will try to drive a specific route that I repeat often with fillups on both ends, and then do the same after I switch.
In any event, if the MPG difference is real or partially real, I may be looking at a non-AT tire for my next summer choice.
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