Help me calibrate my Scangauge! !

I got a 2013 DCLB Sport 4x4 with 30 K on the clock. As soon as I got truk I ditched the crappy stock wheels and added some 265 70 R 17 KO2's.
Got my Gauge all set up, ran a full tank and observed mpg vs tank mpg of the computer was almost 2 mpg.
Does anyone know the size of stock Sport tires? I know I need to know size of original tires to calculate percent difference I'm size so I can start to calibrate.
Also, if I get 18 mpg, I should actually be getting slightly more mpg since I have bigger tires correct? Thanks!

 

https://www.scangauge.com/download/1271/

 

This tool will tell you the diameter of your stock tires.


https://www.tacomaworld.com/tirecalc

 

Follow the instructions on adjusting to get the SG odometer function to minimum error, not the speedometer. Also, depending on how worn your tires are, the original size of your tires may/may not help, plus you may want to adjust your SG every 10,000 miles or so to account for tire wear. Either use mile markers or GPS (compare at a minimum 25 miles, 50 is better) to set the SG % odometer error.

You also should adjust your SG fuel % (compare SG gallons used to what the gas pump says). I compared 3 - 4 tanks and called it good. Be warned, if you change your type of driving, say normally 50/50% city highway, and do a long highway only trip, you will probably see a little difference in SG accuracy, just the nature of the beast.

 

Thanks, everyone!