"Tanks on both" checklist item

Also, why is the fuel selector set to one tank during refueling? Is
it to minimize crossfeeding?

Yep. In my Maule, the lower tank will overflow through the vents if this is not
done. My 150 (which didn't have the option of selecting tanks) would do the
same if the vented tank was the lower one. Note that my Maule will do this even
if the selector is set to "off". Dunno if that's the case with a Cessna.


Would you mind re-explaining the mechanics you just described? I
don't get the "overflow through the vents" part".

Thanks a bunch,
Alex