I have sight gauges visible at just above eye level. The fuel is either on or off, and although it doesn’t feed very evenly, when no fuel at all is visible in straight and level flight there is a generous hour remaining. Between that and knowing the fuel burn accurately at cruising rpm I feel comfortable with fuel management. From experience, not the POH, which is about as useful in a Cub as a chocolate firewall. What is usually the limiting factor is bladder capacity.
I would never do significant flights without a fuel totaliser.
The problem is that without one, one has uncertainty in both the fuel remaining, and the fuel flow. Both gauges are inaccurate. The POH fuel flow figures cannot be used reliably because they rely on a specific MP being accurately set (so, how accurate is your MP gauge), a specific RPM (how accurate is your RPM gauge) and peak EGT (do you have that instrument?).
A fuel totaliser gives you both fuel remaining and the current fuel flow, to about 1% accuracy. The instrument costs about $1000, the transducer and pipework about another $1000. It makes no sense to spend any money on anything else, before putting one of these in.
If you e.g. take a TB20, which has a zero-fuel range of about 1300nm, and throw in the European airport/avgas situation, you have a useful range of say 900nm, and often a lot less. Then throw in a 10% fuel flow error and it gets less still. Eventually, if you don’t have reliable instrumentation and are working just from the performance and the POH, you probably have a 600nm aircraft, which is a bit of a waste.
On the later TB20s (the GT and some before that) one has capacitive gauges which are very accurate. Mine are probably within 2-3% i.e. the thickness of the needle itself. I normally run down the left tank about 1/4" below the right one, if flying alone, and that keeps the aircraft balanced. After that I switch tanks about every 30 mins, to keep them like that.
There is a POV that one should run one tank dry. I’ve never actually done that; instead I wait for the low fuel warning to come one, which happens at about 8 USG (in that tank), and then I burn off another 4 USG from that tank, and then don’t use it again. So maybe 4 USG is “wasted” but equally it is in there for emergency use.
Always depart with full fuel, tank change every 30 minutes – works for me.
say your pre-flight does not show any blue streaks on the lower side of the wing, and say the tank caps are secured (easy to see on low wing airplane), what reasons could there be that fuel gets sucked out?
I’d recommend looking closely at the construction of a Curtis fuel tank drain valve, and in particular the one tiny, fragile rubber o-ring that stands between ‘leak’ and ‘no leak’.
Then count the number of Curtis drain valves between fuel tanks and the location of the flow meter. In my case its three… I think the best plan is (1) understanding the system, the fuel gauges and the little tiny o-rings 
(2) time on tanks, (3) totalizer, and (4) engage brain to alarm when something seems wrong with any of the above.
A guy I know took off in his Rocket a year or so ago Link and saw fuel gauges dropping. He called a friend to have a look and he was streaming fuel from the firewall. He returned to base but when pulling power on final the exhaust lit off the fuel. He landed with zero forward visibility due to smoke, jumped out and the plane burned firewall forward before anybody could put it out. The problem was one loose fuel fitting, left that way by mistake after maintenance. He’s hoping to rebuild the plane when time allows, and he’s not flying my employers biz jet around.
Achim, say your pre-flight does not show any blue streaks on the lower side of the wing, and say the tank caps are secured (easy to see on low wing airplane), what reasons could there be that fuel gets sucked out? I understand that a fuel leak could develop while in flight, but how likely is this, in light of a thorough pre-flight? I am asking because I am torn between just depending on the totalizer or spending a few hundred and have my inaccurate fuel gauges overhauled. Regards!
Flying the piston type that Jason describes, I do two things: I write for my next waypoint the amount of fuel I’m supposed to have left when I reach it; and when I get there, I write down the actual time and the actual fuel. I write it in L+R=T format (Left Tank, Right Tank, Total). My gauges just aren’t accurate enough for proper management; although they get better as the tanks empty themselves, so that’s part of the check.
Changing tanks based on time doesn’t tell you how much is in the tank though. It just avoids an imbalance. Without a totaliser it is the best you can do though.
I use the Garmin (430) reminder every 15 minutes, no chance to forgett it.
That said, I learned to fly on PA28s and my instructor taught me simple trick: switch tanks according to the minute hand on your watch. IOW, right tank from 1-30 mins past the hour, left tank 31-60 minutes. Rinse and repeat. Simple and works well to avoid imbalance.
That’s exactly what I do. Sometimes I miss the change by a few minutes, but it usually balances out.
Having said that you tend to get to know the fuel gauges if you fly it regularly. If you so them drop very low when you wouldn’t normally expect it, I’d land asap and check. As achima says……there are lots of ways of losing fuel and not know it.
