Is the gas engine really on?

Be aware, the Scangauge II DOES NOT always display fuel use correctly. I often see 0.02 l/hr when I'm stopped and the engine is not running. I think the Scangauge adds a little to compensate for better accuracy in long term fuel economy readouts so will indicate fuel use when there is none.

At any rate, don't rely on the Scangauge readout to be completely accurate at all times. There is also almost always a small time delay (the Scangauge displays the data that it receives on the OBDII buss, which often is delayed - hey, it's not a supercomputer in the car! ).

 

Mine is set for Gallons/hr. When stopped it usually displays 0.00, but pretty often displays 0.01. Generally it does not change until the engine starts again. As I've not seen values I believe to be valid between 0.01 and about 0.15, I've not had any trouble interpreting 0.01 as 0.

I suspect some element in the communication path stops providing updated values when the engine stops, so the last value continues to display.

Generally it appears likely to me that for primary parameters SG2 is transparently passing on what it is told by the car. I've used mine on my Audi A4 which itself displays a lot more parameters than the Prius does. For several the values on the SG2 display are obviously much less smoothed than those on the instrument panel. Obviously for derived parameters (such as most of the trip meter values), the question of how SG2 integrates and smooths (if any) is of interest.

But as to your basic point of SG2 displayed values not being completely accurate at all times, of course I agree. Nothing is, including posts made here by senior members.

I wish it remembered the display update rate. I prefer "fast", but it seems to forget that. For watching things such as horsepower, traction battery current, or rpm that makes a considerable difference in utility.