If you are in EV mode you are really getting unlimited miles per gallon, so what number does it use to average? Is it 99.9?

The computer isnt taking multiple fuel efficincy readings and then averaging them together.

The computer is measuring the total distance, and measuring the total gas used. So the distance goes up, but the fuel stays the same.

The number maxes out at 99 mpg, so even though you might be over that number for a while you will still show 99. However, eventually your average will pull down, and the "extra" milage you had when you were in EV is not lost, its averaged in, because again, its not instantanious measurements, its one big measurement

It doesn't compute an average using the current MPG. The computer keeps track of miles (km) driven and gallons (liters) of fuel used and then divides to get the MPG since reset. 99.9 is just the highest MPG the display is programmed to handle.

JeffD

Yep that makes sense! Thanks

I assume that the trip computer (miles to empty) uses some sort of weighted average where the most recent mileage is given more weight that that at the begining of the tank. If that is the case, then the computer must do some additional calculations to keep track of recent mileage, maybe not instantanous mileage, but very recent.

I see no reason to make that assumption. For weighted averages you have to worry about things like the weighting and divide by zero for periods of EV mode. If it just keeps track of total distance, total fuel then the calculations are greatly simplified.

It's all moot anyhow as it would be relatively easy to program either way. I think what's available at the sensor outputs is more of a consideration anyhow.