One of those 'never again" sort of things...

not a dramatic story, but one worth telling...

I was flying my bird over to another airport for the annual. Was
planning on replacing the right fuel cell so at the end of the
previous flight I topped off the left side only (figured I'd burn
off the rest on the way over there). Lo and behold I forgot to shut
off both fuel valves (left them in the both on position.... tip
tanks conversion on the Comanche allows for both thanks being "on").
So when I checked the tanks this AM before departure I had two tanks
3/4 full! Hmmm fuel had magirated from the full tank into the nearly
empty tank. Oh well, I'll have to fly around for 70 minutes to burn
off some fuel.

Set the timer for 70mins before take-off and go cruizing around....
Timer has 5 minutes left.... Radio calls... set up for 45 degree entry
to downwind at dest... then downwind and GUMPS check except for
switching tanks (I figure what the heck, the tanks needs to be
nearly empty anyway). touch down taxi to maint hangar and shutdown.

Meet my IA, we go to lunch... we come back, he wants me to run it
up to warm it for a minute (prior to compression check) test the mags
then shut it down. I crank it up... start to taxi to turn it around
to position so we can back it in the hangar and the engine dies...
TOTALLY out of fuel in the right tank! I literally had 1 minute of
fuel left in the right tank. Great calculation on my part but DUMB
decision to skip the "G" on the gumps check.

Moral: don't try to be so slick.... Live for another day and fly again.