In article ,
wrote:
Years ago we wanted a fuel dipstick for our Cherokee 140. One thing we
quickly found out is that dip indications are very sensitive to the angle of
the dipstick. Tilt it a bit and reading can be off by a few gallons,
especially when below half full.

It's operating on the same principle as the paint stirrer, so they both
need to be inserted consistently into the tank. I use the back edge of
the fuel filler neck as a reference. What the dip sticks DO suffer from
that a paint stirrer doesn't is "bounce". If you dip the tube in and slap
your thumb over it quick it will not have had time to fill. If you wait
a second it will overshoot and then bounce back down. It happens no matter
what the level of the tank but it's hard to see when the tank is half full.
I wait a full five count after dip before putting my thumb on the end.

--
Ben Jackson

http://www.ben.com/