[xbowner?]

The way I calculate mpg is fill up, keep receipt that shows gallons purchased, reset odo then wait until the low fuel light comes on. Write down the miles off of the odo you reset when you fueled up. Repeat this two or three times. Then do the math. I came up with 27.5mpg and the xB says average is 28.3mpg. So yea, the xB is off a little bit.