[brucepick]

(Sorry - I haven't used an UltraGauge so I don't have specifics on that. But I think the fuel + distance input data are distinct for UG, just that the fuel input is from a different source than with the MPGuino.)

I've been considering as separate, the MPGuino calibrations of distance and fuel quantity.

The distance calibration should be pretty consistent, I would think - actual distance would decrease slowly as the tires wear down. So far I've calibrated the MPGuino by GPS before each annual Green Grand Prix so I think that's good enough. I do use the Guino distance readings for my fuel log.

I found that fuel quantity accuracy seemed pretty consistent - until I did some minor injector maintenance (notes below). Prior to that, the MPGuino "measurement" of gallons used was generally within +/- 0.1 gallon of the actual that I pumped. That was as long as I used the same pump, same station, same fill method. For me, that's a 2/3 squeeze until about 1 gallon before anticipated click-off. Then 3 seconds per 1/10 gallon until it clicks off. That's pretty darn slow, and seems to fill it nearly to the top of the filler neck.

About a month ago I decided to run some Seafoam through the gas tank. I included the Seafoam qty in my fuel consumption. Since then, the car takes slightly more gas when filling than the MPGuino estimate. I'm theorizing that the Seafoam cleaned some crud from the injectors, which now squirt just a tiny bit more fuel per microsecond that they are pulsed open. I'm still accumulating notes on this apparent fuel increase so I can dial in a correction in the MPGuino. HOWEVER this deviation doesn't affect my gas log or the Team Competition, because I always record the pump gallons data in the gas log. I just record the MPGuino "estimate" fuel in the notes, for use later in calibrating a correction for the MPGuino. I don't record the Guino estimate if I have to fill at another station or if there is anything else that would make the fill "atypical".