Originally Posted by drozzin
We are not talking about physics here. We are talking about some particular observations.
So no one HAH owner has Scangauge?
Dude - ScanGauge (and the built-in trip meters, and OBDII scanners) derive MPG by measuring injector pulse width, engine RPM, and road speed, along with car model, where they get the injector flow rates. These numbers come from monitoring the data stream from the OBD port that car's ECU feeds. Low road speed, high RPM, and wide pulse width = very low MPG. Perfectly normal, and any "instant" computation will give you the same number, because they all derive it the same way.