Just for clarification, I am not adding an auxiliary tank, but replacing the OEM tank (34 gallons) with another midship 56 gallon tank. The original fuel sender unit will be used with the new tank. So, if as you say, the fuel flow is metered and measured, that should remain the same. And if the fuel level is read as a percentage, based on the float position, then the fuel gage should remain "accurate," as well. My concern is with the average mpg and the fuel range display. Guess I'll just wait and see once the tank gets installed (next week, maybe). It's not a big deal, I just kind of like looking at it, from time to time.