"Neil Gould" wrote:
At most all you've learned is what the fuel capacity of your tanks are,
and that could be more accurately established while on the ground, FWIW.
In fact, the POH should suffice, unless you intend to violate FARs as a
regular practice.

What FAR says you may not run a tank dry?

Given that "how much fuel you really have in your tanks"
is only one factor in how long you can continue to fly, and that those
other factors aren't addressed by running your tanks dry, what *is* the
point in doing so?

Assume you are flying something with two tanks and no "both" position on
the fuel selector. You're 30 minutes from your destination, which would
you rather have: an estimated 30 minutes of fuel left in each tank, or have
one tank dry and an estimated hour's worth in the other?