I made a bench mark on the way home today. The air temp was around 55 and I commuted my normal 55 miles home with a UG reading of 40.6mpg!
I'm confident the gauge is accurate as it has typically matched or been within 1/10 of the miles/fill-up calcs.
The car ran at 100 to 110 deg intake temps and 212 to 217 coolant temps.
The last part of the trip is the conjested part of the commute and the pucker factor was pretty high when I started to realize how close the 40 I was getting.
WOO HOO!
I'll have to let this settle for a bit before setting a new bench. .....maybe the 40mpg tank average. I think it is within reach as the air temps come up.