Don't know if this is common knowledge but I wanted to know, by changing tires, how I could figure out gas mileage and if it made a difference enough to bother w/ calculating it.
Found a tire math page on Discount tire and it's pretty easy to do. Basically you type in the stock tire size and what you put on and it will tell the dif in revs and in. per revs. Anyway you can play w/ it and see for yourself.
I myself came up with what I think is a basic finding of: for every 100 miles I'm a 1/2 mile less. Not enough to worry about. That's a whole 1 1/2 per tank. Coarse you all could one up me w/ the width, tread, etc. into the equation.
See what you come up with.
If you need help, let me know.