Originally Posted by pdrunk
The UG keeps a running count of distance travelled. By inputting gallons used, it divides its distance by your gallons, giving MPGavg.
If you forget to zero distance travelled at each fillup, distance constantly increases, increasing, falsely, MPGavg.
When i forgot to zero distance on my first fillup, all my numbers jumped up dratically at the second fillup/calibration. I had to start the whole calibration hing all over again.
Only because you didn't add your previous fillup.
If you zero every time you get gas, then you are constantly resetting it.
You'll eventually sneak up on a good calibration, but it may take longer.
If you don't zero, then you simply have to add your previous tanks to the current tank to get the proper correction factor.
Like I said... Yesterday I filled up and recalibrated with 57.4 gallons.
That was 4 tanks. That's exactly what the instructions that the OP posted say to do.
Hint... When you go to the calibration screen and you see "32.503" already there, you should not change it to "16.538" that you got on that fill up... you need to add the previous fillup to the current.
I save my outgoing Fuelly text messages for a month or so, so I can go back 5 or 6 tanks and add totals if I want to recalibrate.