How bad did tires affect milage on an Ecoboost

[MORSNO]

Tire size 275/55-20 275/60-20
Section width 275 mm (10.8'') 275 mm (10.8'')
Sidewall 151 mm (5.9'') 165 mm (6.5'')
Tire diameter 810 mm (31.9'') 838 mm (33'')28 mm (3.5%) taller.
Circumference 2543 mm (100.1'') 2631 mm (103.6'')
Revs per mile 632.8 611.6
Speedometer When speedometer reads 60mph (96.6km/h) actual speed will be 62.1mph (100km/h): 3.5% faster.

 

[Chadx]

275/55r20 vs 275/60r20 is that much difference?

No. I was addressing the original posters (note the sizes in my post were comparing stock to his 295/65-20). The others ran your numbers and posted the websites they use for conversion. I, too, was using http://www.tacomaworld.com/forum/tirecalc.php when I canulated the OPs numbers. It's handy so you can run your own numbers.

 

[live2rideyamaha]

tire size

the factory size is 275-55-20.
thanks for calculating that I figured it was off a little but that is quite a bit.
thanks for the help and dicussion guys.