In article ,
says...

I understand that there are various obstacles
to having reliable fuel quantity indicators in a light aircraft, but I
bet that it must be possible. How difficult and expensive would a good
one end up being, and what would it look like?



I don’t know if it still holds true, but as of a year or so ago, Flying mag
indicated there had not yet been a fuel exhaustion accident in any of the new
(post 1998) Cessnas, with improved fuel gauges and low fuel warning lights.

The "old-style" gauges were considered by many to be unreliable. I’m not sure
they were as bad as people claimed - they flick on and off frequently, but you
can usually tell when it is indicating something meaningful and when it is
just off. I can imagine if you fly down to very low levels (guessing here,
because I’ve never done this) the distinction may not be so clear, and
repeated lore has it that pilots have flown the tanks dry thinking their
gauges were simply inop.

I learned the same as most here, to calculate time based on known quantities,
reliable fuel burns and to use dipsticks as well, however I agree with -a-
that an unusual fuel burn or a leak can only be detected if you have
instruments you can trust.
There are fuel exhaustion accidents that result from other causes than running
dry as well. Taxying out on the AUX tank to make sure it is working is a good
idea, but not possible in all planes. Some aircraft return part of the fuel
from the aux tanks to the mains, so you can not switch to aux before burning
away some of what’s in the mains, if they are full. Other planes have tip
tanks which cannot be accessed if you wait until the mains are dry and a vapor
lock develops. Planes have crashed with ample fuel reserves that pilots have
been unable to access (or didn’t know how).
Fuel management in small planes deserves some thought above and beyond the
simple question of "having enough". Switching tanks in flight is usually a
trivial affair, but sometimes meets with unexpected results (blissful
silence). Good idea to give some thought to when and where you are going to do
this, and what options are available if it goes awry.