Quote:
Originally Posted by RobertSmalls
No, the ScanGauge can't measure fuel consumption. It guesstimates it based on the amount of air entering the engine, which it infers from MAP and RPM, or MAF, which it only reads once a second AFAIK.
It's the best estimate available over the OBD-II port, and it's usually good enough unless your car varies the air:fuel ratio. On my lean burning car, I don't even bother using the ScanGauge for mpg.
|
Bingo. Air-fuel ratio is the key here. That's not reported to the OBD port, so it can't accurately calculate the fuel usage. I'm sorry, but it's not likely to ever be quite right with your diesel.
On my gasser, once calibrated, it's very accurate. It's been accurate to within a half gallon
total over the last 2 years. One tank might be a half gallon high or low, but that's all from the pump. The next fill balances it out. I trust the Scangauge more than I do the gas pumps.