[98xlt]

So I switched my evo out for a CS in order to get custom tunes. I don't understand the average mpg feature on the CS. It used to work great on the evolution, but on the CS it doesn't seem to make sense- When I am idling, the avg does not go down. It only changes when I am actually moving, which is leaving out a serious part of the equation. When I sat with my evo the avg steadily dropped. I know you have to manually enter your last fuel economy, and i did, but i don't know why it can only produce a misrepresentation of the numbers when my evo worked fine automatically. Is this just my unit or what?
98 4.6