I also have low fuel warning lights, but they come in a different levels for each tank! They only way to get the most from a tank is to run it dry, and you will get more than the useable fuel limit if you do it in level flight. I'd try it over an airfield in good weather just to see what happens.
A sad situation would be where you had low fuel spread over 2 tanks and a go-around causes unporting and engine stoppage even though you theoretically had enough fuel.
I have to say I would never do any serious flying (I mean anything beyond Shoreham to Lydd) without a totaliser.
I actually do relatively few of my really long flights (I just write those up so people think I do them all the time 
) but if you have a totaliser, you can confidently do say 5 flights whereas without it you would do only 3.
On the scale of aviation eye-candy money-burning, a totaliser is really cheap. The instrument is c. $1k, the transducer is c. $700, and you have maybe $200's worth of hoses and fittings. The installation is trivial; you just follow the STC or other type-specific instructions.
The other total no-brainer is an EDM700 (or similar).
A sad situation would be where you had low fuel spread over 2 tanks and a go-around causes unporting and engine stoppage even though you theoretically had enough fuel.
True, though (with 2 tanks) you have cut things a bit too fine then, already. However I think if I was facing a potential disaster then I would run a tank dry.
My numbers suggest the stop at Alderney is probably worth it financially, but not in terms of time and hassle.
Good point about the duty drawback, but group central funds get that - not me! Fuel purchased away from EGLM is reimbursed at the EGLM rate. So I can save 50p a litre at Alderney, and potentially be out of pocket at Angouleme depending on what the price is.
As I said, I don't have a totaliser and it being a group we are unlikely to get one just because I want one. Incidentally, when using a totaliser how do you know how much is really in the tanks at take off, unless they are full to the brim? Dipsticks can't be terribly accurate.
I will probably stick to my one hour of fuel remaining rule. Though as someone pointed out it really depends on where you're flying.
when using a totaliser how do you know how much is really in the tanks at take off, unless they are full to the brim?
That's about it, yes...
The marks on the tabs in the TB are very accurate though; probably better than 0.5 USG.
When I used to rent out my TB20 I had one renter (an instructor, with a fake ATPL no less) who used to fiddle with the FOB value, to get a reduced fuel invoice from me. And that is a vulnerability in a shared environment... in the same category as using the (tamper-proof) HOBBS time for billing, when using pure airborne time is more fair, prevents people rushing the preflight warmup, etc.
Also, 1hr is a bit close in a 100-150kt plane, if there are any persistent conditions (fog, etc) forecast.
I fly a Cessna 172M with the usual Cessna fuel gauges and no totalizer and a Cessna TR182 which has everything that Peter mentioned.
Of course I like the fuel totalizer but it is not essential. My C172 has a safe endurance of 4:30h and I fly legs of up to 4h with it. I check the fuel quantity with dipsticks and make sure to always lean to peak EGT and fly the same power setting. If I ever forget to lean correctly, flying for 4h could push it to the limit and I'd not get any warning.
I think the safe endurance / known power setting / dipstick method is adequate for most GA aircraft.
The fuel totalizer is very useful for longer IFR trips where unexpected level changes (I have to climb full rich at ca 100l/h) can make a difference.
As everyone has been saying it depends. Across the Atlantic you have a very different view of this compared with crossing France. I normally think of it as 1 hour but unless weight and balance was a big issue always fill up.
Coming back to the UK from Cologne last winter (he says somehow implying that we are now not in winter...) the entire south was fogged in and there was chaos. I had planned to divert to Manchester but actually made it in to Oxford in minimum but legal visibility. It was a very nice feeling though knowing that I had fuel to get back to Cologne if I needed to.
In real IMC I don't like fuel coming into my worries.
I think it is much harder in a rented aircraft as I know how much it takes - exactly. How much I have used (totaliser). But I also always write down usage and time on tank switches as a backup. The totaliser has always been right but I never know if I could lose the MFD on which it appears.
It is tough though to follow a totaliser and known fuel reading when a fuel gauge shows a dramatically different number. Particularly as happened to us between Iceland and the Faroes. One meant we would make it easily with reserves including alternate, the other didn't. You recheck your numbers quite a bit when that happens.
As some people have already mentioned, it is also my experience that the most impotant factor when planning flights towards the "low end" of your fuel tanks is to know the exact quantity of fuel that is is your tanks at the start of the flight. A huge confidence booster.
The worst case is when - and I think that's a quite typical scenario - you fly, say, an old club C172 and the visual look into the tanks, as well as the fuel gauges, read "roughly one third" (with no clue if it's really more towards half full or towards a quarter full. No dipsticks or similar abailable. Now, if your destination with cheap fuel is one hour's flying away, what do you do? Add some more of the expensive fuel for safety? Or would that be over the top? (I am sure many have been in this situation).
There are basically three ways to determine your exact fuel amount in the tanks:
(this only works when only yourself fly the aircraft): detemine the last time the tanks were topped up, then subtract the flying time multiplied by hourly fuel burn. Again, if only you fly the plane (in which case you normally know the average fuel burn very well), this can be very precise. Only downside: a fuel leak can go undetected, as well as a recent fuel theft (fuel thieves normally take small quantities at a time, say 30 litres, in order to remain non-conspicious). And: important not to f**k up the math! ;-)
(this is actually very similar to 1.): a fuel totaliser/fuel computer. The one in the Cirrus is awesome. Same downside of no. 1. though.
...and that is really the very best thing, even though it sounds so low-tech: get a calibrated fuel dipstick and measure the fuel that is actually in your tanks. Along with my Cirrus, I also often fly club Cessnas and I can really say that the few euros I invested in calibrated fuel sticks for the types that I fly was the best money I have spent in a looong time. In the past, I didn't have fuel dipsticks and I was permanently in doubt about the exact amount of fuel I had on board... in the end, I often wasted loads of money by flying with much too much fuel in the tanks, because I was - and still am - terrified by the thought of of running out of fuel on a sunny day with a (mechanically) perfectly working Cessna. Now that would really look bad, especially for a flight instructor...;-)
Now that I always know precisely how much fuel I have, I confidently go down to a lower "nominal" minimum fuel than before - just because the previouly huge incertainty factor has almost vanished. That number - your personal minimum fuel at arrival - obviously changes with every flight, because every flight is different.
[Please don't use the F-word here]
An anecdote, which made me increase my reserves a bit.. Flying to Reus from Mallorca one day, flight time less than an hour. 1 hour reserve would be OK in my mind, perfect weather, and worse comes to worse alternate 20 minutes away. Approaching the field, 'all stations hold over xxx', plane with flat tire on the runway, expect 20 minutes delay'. As I was one of the first in line I did not think much of it. Sure enough, I landed within 15 minutes, but there were already quite a few light planes circling around (and a Ryanair one too, but they care a lot of fuel, so no worries for them ;) ). Anyway, while landing I thought to be helpful and brake briskly so to make the first exit to make room asap. Yep, you are guessing right.. Your truly blocked his mains, and one tire blew.. The controller (keying his mike by mistake) 'Oh s.it, not another idiot'. Long story short, some were holding for 40 minutes and must have been making quite some sums about a cut-off time to divert. Ryanair? They landed on the taxiway of course.. :)
To maximise the saving, this obviously requires landing at EGJA with as little fuel remaining as possible.
A some died from trying to maximizing this principle.
Yep, I'm aware of that possibility. Which is why I asked the question about what people are comfortable with.
I'm not talking about eeking out every last drop and having the engine splutter and die as I roll up to the bowser, I'm talking about arriving with 30, 45, 60 or 75 mins fuel remaining - that sort of thing.
