Technical how big is my fuel tank? (How wrong is my gauge)

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Technical how big is my fuel tank? (How wrong is my gauge)

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My Panda 4x4 Multijet is supposed to have a 37 litre tank (which is about 8 gallons), so far as I know. Given that I am averaging 55 miles per gallon, I should be able to go well over 400 miles on a tank.

Not just once, but several times now, when the gauge still shows a quarter full, the 'range' display goes to '---', and the 'Warning - low fuel' message appears on the screen, about 330-350 miles after a fill up. Very soon after, the yellow 'low fuel' light comes on and the gauge drops to the last bar (the divided one). Even after driving 20-30 miles more, when I fill up I can only just squeeze around 31 litres in, which suggests that either the gauge and warnings are wrong, or that the tank is much smaller than I think...

How's this compare with others' experiences?
 
I've found that ever Fiat I've driven has been very pessimistic when it comes to low fuel warnings. More than once (in the Sei with a 30l tank), with that light one, I've gotten 30+ miles out of it. If you're only getting 31 litres in, then you've got at least another 50 to go before you really need to fill up. Play a round of fuel light roulette, what's the worst that can happen? ;)
 
It's not uncommon for fuel gauges and Range displays to err on the side of caution, as it avoids any potential law suits when someone gets dumped on an empty road en-route to hospital to have a baby when it says they should have made it ..... That's why the Range goes from 30miles remaining to Zero in one hit, to prevent the issues of having it say that there are 5 miles left (hospital 2 miles away) and then it stops....

This is designed into the systems and seems pretty common in modern cars. My TA 4x4 has a 35litre tank and I squeezed 32 litres in one day last week having driven about 20 miles on "---" range after about 290 miles total, so there was still a little over 1/2 a gallon left in the tank.

My Morgan 3-Wheeler however says it has 0% left (it's in percent on the gauge, just to be different) after only using 22 of the 42 litres available, which is really really annoying - but then it is a Morgan, so that's to be expected as well :)
 
Doesn't sound too far off to me. The light comes on when there's 5-7 litres left according to the handbook & you're within 1-2 litres based on the info in the first post.

In my experience the display in my AGP goes to ---- from about 40 miles on the countdown. This annoys me, but there is a logic to it - how many people will rely on it and run out of fuel if it counted down to zero? You can hear the complaints - "but it said 2 miles left"!!

I'd run it for 50 miles once the yellow light comes on & then see how many litres you can get in. It is a gamble though, but fun.... (y)
 
R1nga is right, have just checked my manual, the 4x4 pandas have a 35 litre tank, not a huge difference I know but could make a 25 mile difference to your range calcs.
 
Funny, but when I was getting the run through with the salesman before I drove off he did mention that you might get the fuel light coming on earlier than you'd expect and that it'd give you my plenty of time to fill up but not to worry too much about it. Ive not had it come on yet but I thought it was a strange thing to mention.

Mine's a petrol with the "smart" filler cap btw and I'm a bit paranoid about the 10 seconds rest after filling up. I'm genuinely concerned about some kind of vacuum or air in the tank situation. The whole concept seems a bit vague to me.

M
 
Sound like the warning message is coming in too early to me.

On all three of my fiats (500, panda and Punto) the warning light comes on first with about 70 miles left on the range and the low fuel warning message comes on at about 35 miles.
 
Thanks to all for the replies

The main point I was questioning was the fact that if the tank is 35 litres, then at the 'quarter' point of the gauge it should have nearly 9 litres left but the 'range' display shows '---' aroudn that point. Even when it drops to the last eighth of the gauge, still over four litres should remain (in theory), enough to still go over 40 miles?

Anyway, warmer weather, and being in less of a hurry (not over 70 on motorway), and less far round the rev counter (not over 2000, except in 5th gear, but still moving off swiftly), the past 150 miles on a mix of motorway, St Albans city centre on market day, fast dual carriageways, country lanes and around town - and the dash is displaying average 59.4 mpg... happy with that!
 
Thanks to all for the replies

The main point I was questioning was the fact that if the tank is 35 litres, then at the 'quarter' point of the gauge it should have nearly 9 litres left but the 'range' display shows '---' aroudn that point. Even when it drops to the last eighth of the gauge, still over four litres should remain (in theory), enough to still go over 40 miles?

Anyway, warmer weather, and being in less of a hurry (not over 70 on motorway), and less far round the rev counter (not over 2000, except in 5th gear, but still moving off swiftly), the past 150 miles on a mix of motorway, St Albans city centre on market day, fast dual carriageways, country lanes and around town - and the dash is displaying average 59.4 mpg... happy with that!

That's pretty good Pete - way more than I've achieved here in the hilly bits of Surrey. Interesting to see that you too can run around at little more that 2000rpm, which really will make a difference overall I suspect. I really must try harder, as my current record (6,600 miles in) is 44mpg.

Had another car serviced this week and was given a 13-reg 500 1.2 Pop as a courtesy car. Hadn't driven one of these since moving my previous 1.2 4x4 on last year and it was an interesting comparison, having got used to the charms of the TA in my 4x4 now. Pulling away fro junctions was often pretty hopeless in terms of response and it's clear that the low-end torque is much reduced over the TA (and I'd say over my old Euro-4 1.2 as well). But even when driven like most hire cars, it still showed 52mpg on the dash display after a 120 mile round trip. If that's a representative figure, then there's no doubt that the ease with which the TA encourages you to drive harder is what does for the MPG. The TA is ultimately a lot faster than the 1.2 in every aspect (as you'd expect from the stats of course), but that fun factor will never make the occasional economy drive any easier to deliver.....
 
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