UltraGauge FE calibration?
 

So, I just had some great insight into the inaccuracy of my UltraGauge in its current form, it appears optimistic... Today I found myself on the Ohio highways on a 680 mile round trip, and since it's flat there, I was getting some pretty friggin awesome mileage for what my car is... I filled up in Sylvania, and drove toward home, and stopped at the last cheap fuel station on the way back, about 65 miles out. This was done in two trips the UG recorded, one trip averaging 44.0mpg indicated, and the other averaging just over 42 indicated... So, had the UG not reset during the time we stopped for food(I kept it running during bathroom stops), it would have shown an average somewhere around 43mpg... When I filled up, the actual mileage was like 38.7mpg... Given that the UG is reading 10-15% optimistic, what's the best method of getting it to report numbers closer to actual mileage? It doesn't need to be 100% accurate, but 10-15% error definitely gives me a false sense of achievement...

At your next fill up, go to the calibration screen. Correct the UG's mileage to match your trip odometer and gas burned to match your pump receipt. Then reset all distances to zero and go about your next tank. At your next fill up, do all this again. Over a few tanks you'll zero in on matching the pump and your odometer. You'll get more accuracy by going longer distances between fills and using the same pump.

Eventually you'll have enough confidence in the numbers to not check again, just reset long trip distance at each fill so it's showing your mpg on the tank, not since some random time in the past.

I checked this, but as it seems, I've done some 30k miles in various vehicles with the UG connected, so the only way to reset that in any reasonable time would be to do a factory reset... Maybe telling the UG that the engine is ~10% larger would help?

I don't think you need a factory reset. I do think Fat Charlie is correct. You should be able to just reset the engine and miles and all that and be good. The califbration Fat Charlie describes works best if you go to the same pump each time, pump on the slowest flow rate, and do it three times. After that go to whatever pump you want, but iunderstand that there is pump variation, and that the UG is only estimating fuel use, so it will vary. Not every variation should result in calibration.

I don't think there is a place in UG to adjust your tire size. Only two things that can be adjusted are Distance and MPG. I can't believe that over 100+ people just bought this thing and yet very few responses on the settings. Maybe people haven't had enough time to play with it. I don't have any mile markers near me either so it's hard to tell what to set the distance for. My speedometer is about 1-1.5 MPH faster than the UG MPH. I think the UG is correct (because it is dead on with my GPS). I'm still not happy with the MPG setting though (I wonder if the truck uses more gas during engine starts and stops) and if so, does UG account for that?

Adjusting reported mileage (as in distance traveled, not mpg) is how you adjust tire size in the UG. If the UG is already calibrated for mileage, then you can calculate the difference in revs per mile of your previous (calibrated) tire size and your new tire size, then adjust the UG accordingly.

Or you can use real numbers to calibrate at your next fill- or do both if you're feeling ambitious, do the math and then verify by calibrating at the pump.