[mrk]

Please tell me if I am wrong, but it seems to me that it does measure instant (and average) mpg

From the manual:

Displayed items are as follow:
ØKPH (MPH): Current vehicle speed
ØL (GAL): Fuel used of current trip
ØLK∮ (MG∮): Average fuel economy per 100 kilometer/mile
ØLHK (MPG): Fuel economy per 100 kilometer/mile
ØXX:XX: Time driven
ØKM (MI): Distance driven
ØKM (MI ): Distance remaining before tank is empty
ØKH∮(MH∮): Average speed
ØKPH (MPH): Maximum speed

And one question about gauges, does SG has more items than Maxitrip??
cheers