driving efficiently

[Ginger]

I don't think that's usually true, most are digital and do it by summing up each firing of the injectors. Very oversimplified, the ECU knows what duty cycle each injector was at when it opened, so it just keeps a running tally of that. It should be, and I've found usually is, a pretty accurate method.

+1

The BMW motorcycle gauges (calculate mileage achieved, fuel remaining, and miles remaining) are accurate down to the mile these days.