Now that I have calibrated mine correctly I can say the Ultraguage was pretty much useless/inaccurate before the calibration.
I have been wondering for a while why my mpg was so bad. Before my tires I used to get very good MPG. I actually thought the 285's would help since I have the 4.10. Over the past couple of months i just pushed the thought under the rug and blamed my MPG results on the tires. (NOT THE CASE)
I had no idea how off the odometer was on my truck after the tire size increase. With this being off it would even through out bad numbers when i calculated my own MPG by hand. Now that I re calibrated the Ultraguage and calculated it by hand again I AM GETTING 19-21 MPG !!! Which i believe is a lot more accurate, I knew something wasn't right
Just to give you an idea of how much it was off I did a longer distance test:
I drove 31.1 miles according to my trucks odometer.
On the same trip my GPS was reading 35.1
In the big picture that is a short trip and 4 miles off can add up over time!
My speedo (on the Ultraguage) is also more accurate. Didn't realize how fast I was really going the past couple months lol.
To get your money and the best experience out of the Ultraguage I highly recommend calibrating it whether you have Factory tires or +/- size tires.