[dcb]

ok, lemme back up a bit. The MPGuino conceptually has three trips, instant (not much of a trip really), Current, and Tank. Each trip tracks fuel used, distance traveled, and time elapsed and we compute everything else from there.

On the custom screen (the default one) has for variables displayed

MG S
GH C

MG is Instant Miles Per Gallon
S is instant Speed
GH is Gallons Per hour (instant)
C is Current Miles Per Gallon.

re "Custom" screen values.

Current will reset after 7.5 minutes of inactivity (and the backlight will turn off too). Inactivity is defined as no speed pulses or injector pulses or button presses for 7.5 minutes (the delay can be changed in the settings). So if the car was off for that long then C would reset.

I found Current MPG more useful than tank, since it is telling me how I am doing on my current trip, and it resets itself so I can try to beat that number on the way home, next morning, etc, rather than at the next fillup.

Speed is of marginal value, mostly I wanted it on the first screen so you can tell if your speed signal is working.

GH is useful, relates to injector duty cycle, and gives a quick "My injector tap is working" confirmation on the first screen.

And instant MPG is pretty popular (though I find the accumulated Current MPG to be a lot more "honest")