Tony Cox wrote:

"Koopas Ly" wrote in message
om...

The only time that fuel is set to one particular tank is on the
ground. I've never used fuel from only one tank in flight. Why would
someone do that?



Some models of 172 *require* you to select a single tank
above 5000', due (supposedly) to vapor lock problems.

Check your POH.


No 'supposedly' about it. Ours locked at 7500' on a humid day because one of
my partners didn't believe it could happen and didn't follow the procedure.
Fortunately an airport was within glide range. Strangely enough, by the
time he landed the engine was running fine again....
--
Frank....H