I was sitting in my car listening to a CD for awhile, engine off, and watched my AVG MPH readout change from 30 to 29 to 28. Dont you think this calculation should only change if the engine is running?? I didnt notice my Avg MPG change (though it may have).

Mark

 

Since the AVG MPH readout is based upon time and distance, it will keep calculating as long as your key is turned to ACC to keep it powered. I guess it figures that if you were on a trip, if you had the power on, then you were still in the car so the trip was still in-progress?

As for the MPG, since you were using no gas, but moving no distance, it would not change unless you started your engine.

 

I have to argue this, my mpg avg changes as long as the computer is activated. The speed will drop slowly and the fuel economy will drop as well. I think it depends on how long you have been logging your mpg avg thou since it seems to drop slower near the end of a tank of fuel than it does at teh beginning of a tank of fuel.