Suggestion for Garage Trip Log page

[101Volts]

For those who drive vehicles that they have no idea what fuel economy they're getting on a given trip (Like cars without fuel injection), How about an "I don't know/Unknown" Selection? As it's been, I've had to post numbers that are only guesses of the MPGs for the trips of the 1984 Chevy; I realize the ScanGaugeII isn't completely accurate either but at least with that I might be fairly close.

Come to think of it, I'd like feedback on this because I don't know if it's a good idea or not since I just considered that the SG2 isn't all quite accurate either especially in the van I drive, Not being calibrated and needing to re-set it if it goes wonky, Etc.