In article .com,
says...


I fly a 172 F.

The fuel selector says to select single tank operation at or above 5000
feet.

If you leave the selector in the "both" position, under 5000 for any
prolonged period of time (couple of hours) the right tank appears to go
down more quickly than the left. This is confirmed at fillup.



Are you sure?
I ask because in the 172's I fly it's just the opposite. The left tank
always goes down faster than the right, and I frequently switch to RIGHT
tank only during flight, to even them out (not that it matters overmuch).
The 172' are of course placarded for use of "both" during TO/landing, but
I have never seen the 5000' placard.

I have heard that the left tank becomes slightly pressurized, due to the
forward-facing vent on that tank, which is why it drains faster than the
other. I do not claim this to be a fact - just something I've heard.

G Faris