How does bigger tires affect gas/speed/display?
 

I'm still new to this... Just put a leveling kit on my 2011 2wd v6 and added 285/65/18 mud terrain tail grapplers on XD rims. Looks great. Went from stock 17" rims and tiny tires.

How much does this affect the speedometer?
Does is change the miles to empty?
Does it mess up the actual miles driven?
I went from 17mpg to 13mpg

Is this much change normal or are my numbers skewed because of the tire size.

I've heard of tuners. Don't know much about them. Has anyone taken their truck to the dealer to set the new tire size?

if u search google ull find bounds of info dealer mite fix but mite as well tune it imho!! :-)

Probably by about 2-5 MPH depending on how fast you are going (depends on your stock tire size)
Yup
Yup
That's about normal.

Close to normal and somewhat skewed due to the change in tire size

Yup. Dealer may or may not be able to calibrate for tire size. Mine was not able to go up to the size I went to. Had to get a tuner to get it right on.

had stock 20's on truck

went to 17 raptors.. mpg shows me 2.5-5mph slower then i am .. so when tach says 60 im doing 65 (confirmed on portable gps)

mpg ehh about same .. maybe a tad lower..

also i can lift a 20 with tire easily .. the 17 rator rim and tire is HEAVY .. and i need to really UMPF it up to lift it
heavy tire and rim mean more to turn .. means less mpg