Changed the stockers out for 285 X 70 X 17 BFG AT. I was curious about calculating my MPG. IfI manually calculate and come up with 14 MPG am I actually getting a bit better then 14MPG or a bit less. Iv also read that some vehicles will auto adjust for slight tire/wheel mods does the 03 fall into this category?

Thanks

 

Because your speedo is showing a speed slower than what you are actually traveling, your odometer is showing less miles than you are actually traveling. Therefore, you are actually getting better gas mileage than you are calculating.

No auto adjustment for tire size changes. Either go to the dealer to be re-calibrated (usually a small $40-$75 fee depending on the dealer, or get you a tuner and have a lot of other benefits too...

 

hammer is correct on this one.... i would reccomend the tuner because it adds some fun and mpg's along with the calibration tool... the superchips are highly reccomended

 

I have 325-60-20 on mine and it threw the speedo off by about 10.

 

http://www.dakota-truck.net/TIRECALC/tirecalc.html

This should help you out in figuring how far off you speedometer and odometer would be.

Just put you stock size for tire A and then your new size for tire B and compare.

 

Your actual miles traveled are more than the odo says.

Your mileage went down, not up.

Bigger tires means more torque to get it rolling and waste more gas.

Time to look into gears.