S80 2010 diesel fuel gauge accuracy

S80 2010 diesel fuel gauge accuracy

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IAmTheWalrus

Original Poster:

1,049 posts

51 months

Monday 29th November 2021
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Hi,

On Friday, floored it home,however flooring it from 0-70 made the miles left gauge go from 150 miles to 110 miles despite the fact I only did 11 miles to get home.

Today I went to work and back, casual driving, and the 110 had just one or two miles into the return tripe went down to 50 on set off and then down to 45 two miles later, how accurate is this thing? I presume its possible some kind of gauge is sticking. I would like to add a bottle of my lucas upper cylinder lubricant which had apparently solved the issue I had similarly in my old BMW, its gauge would fall quite unexpectedly near emptying scenario until I fill it up and it seemed to make it work more accurately.

Anyway I don't trust a digital gauge, perhaps because I am new to it, so was just wondering do others trust it? I don't understand how it can go from 150 miles to 45 after a mere 35 miles of driving.. Can I use lucas upper cylinder lubricant in this car? Thanks in advance.

IAmTheWalrus

Original Poster:

1,049 posts

51 months

Tuesday 28th December 2021
quotequote all
OK so further to the above, I filled up the tank and added lucas upper cylinder lubricant hoping this might make the fuel gauge less sticky, I have driver well over 100 miles since and it seems to show full still? The average mpg shows 40mph but the actual live one shows 50-60 and yet the only time I am driving inefficiently is like half a mile to the main dual carriageway where I promptly go up to 60mph for the rest of my 11 miles drive so not sure what's going on there.

pobot

57 posts

69 months

Tuesday 28th December 2021
quotequote all
Have you read the manual? It probably says something like:

"The calculation is based on the average fuel
consumption over the last 30 km and the
remaining driveable fuel quantity"

Davie

5,022 posts

222 months

Tuesday 28th December 2021
quotequote all
I can't decide if this is trolling...

The range left is variable and calculated on the past XX number of miles Vs fuel used so if you've been trundling Ali g at 56mph then it may say 1/2 a tank will give you 500 miles range but if you then start driving Luke a tit, obviously the instant MPG will plummet, the car will hastily recalculate the range which could now be say 250 miles on the 1/2 tank assuming the current driving style continues. Start driving like a nun again and it'll recalculate and your range will likely increase.

Also the on board computer is rarely bang on with real world MPG, it's usually a bit optimistic and so that will in turn skew the range and such like so hence they're always cited as being for guidance only and I wouldn't be running it to 5 miles remaining and thinking it's actually telling the truth... its not. Ditto the fuel gauge... when the last bar disappears, you don't just run out and stop.

Don't worry about it.

IAmTheWalrus

Original Poster:

1,049 posts

51 months

Tuesday 28th December 2021
quotequote all
pobot said:
Have you read the manual? It probably says something like:

"The calculation is based on the average fuel
consumption over the last 30 km and the
remaining driveable fuel quantity"
I've been driving the car for the last four weeks at over 100 miles a week so kinda beyond 30km and come to think of it I do over 30km a day. Imagine currently more concerned about the image of the bar showing how much fuel is left so I can safely plan the fuel station visit..

IAmTheWalrus

Original Poster:

1,049 posts

51 months

Tuesday 28th December 2021
quotequote all
Davie said:
I can't decide if this is trolling...

The range left is variable and calculated on the past XX number of miles Vs fuel used so if you've been trundling Ali g at 56mph then it may say 1/2 a tank will give you 500 miles range but if you then start driving Luke a tit, obviously the instant MPG will plummet, the car will hastily recalculate the range which could now be say 250 miles on the 1/2 tank assuming the current driving style continues. Start driving like a nun again and it'll recalculate and your range will likely increase.

Also the on board computer is rarely bang on with real world MPG, it's usually a bit optimistic and so that will in turn skew the range and such like so hence they're always cited as being for guidance only and I wouldn't be running it to 5 miles remaining and thinking it's actually telling the truth... its not. Ditto the fuel gauge... when the last bar disappears, you don't just run out and stop.

Don't worry about it.
You can't decide if this is trolling???

https://dictionary.cambridge.org/dictionary/englis...

"the act of leaving an insulting message on the internet in order to annoy someone"

Exactly who am I insulting in this thread?? How is this possibly annoying?? Exactly how did you come to the conclusion that it might be trolling just because I'm pointing out after one hundred miles the fuel counter is still on full (basic mechanics problem my friend) and my only concern is I will be running out of fuel in the middle of nowhere because I trusted the fuel gauge?? Both ends of the fuel measurement is problematic. Yes I agree the estimate for fuel use is going to be dependent on the driving style however my driving style is the same for the last few weeks, I am just commuting to work at a steady space.

Davie

5,022 posts

222 months

Wednesday 29th December 2021
quotequote all
I probably shouldn't bite but I'm still undecided if you're playing at it or genuinely not understanding how the car calculates the range remaining based on the MPG it's doing and how much fuel is currently in the tank but given that it went from 150 miles to 110 miles having been floored from 0 to 70, yet you only did 11 miles suggests you maybe don't understand how the range is calculated. Drive to work tomorrow like a nun and your range may actually increase... or reduce but at a much slower rate.

As for the fuel gauge and the accuracy, I'm fairly sure it's a 70 litre tank but I'm also pretty sure that if you put exactly 70 litres in and the sender was sat at 100%, thus indicating full on the gauge... you'd easily get another couple of litres in there before the nozzle tripped. So that couple of litres will get you a reasonable distance, then you'll still have 70 litres and 100% via the sender and plus the digital display isn't progressive so you could use another say 5 to 10 litres before it'll then drop to the next section of the display.

It doesn't sound like anything is wrong, be it with the range or how it's changing depending on your driving style and a gauge that sits at full for a reasonable amount of miles before it starts to drop isn't an issue either. As for your average MPG differing from your instant MPG, again I'm not sure if that's how it's worded or if you're not differentiating between average and instant? Either way, you can check all of this with VIDA or go old school, fill the tank, do 100 miles, fill it again and work out your real world MPG as generally speaking, the computer isn't always accurate but not to the extent where it'll suddenly run out of fuel without sufficient warning.

Best of luck with it, but it's probably best I do a Ducan Bannatyne from here on.

IAmTheWalrus

Original Poster:

1,049 posts

51 months

Wednesday 29th December 2021
quotequote all
Well thank you Davie,

The extra couple of litres being in the tank would make sense.

I am indeed trying to do it old school, I filled with £104 of diesel and reset the trip computer.

Davie

5,022 posts

222 months

Wednesday 29th December 2021
quotequote all
IAmTheWalrus said:
I filled with £104 of diesel and reset the trip computer.
Even though I've done it a few times myself, the shock of spending over £100 to fill the tank doesn't get any less!



IAmTheWalrus

Original Poster:

1,049 posts

51 months

Thursday 30th December 2021
quotequote all
Davie said:
IAmTheWalrus said:
I filled with £104 of diesel and reset the trip computer.
Even though I've done it a few times myself, the shock of spending over £100 to fill the tank doesn't get any less!
To be fair, I the less time spent a the fuel station the better, I had a BMW 320 coupe which was converted to run on lpg, its tank was in the wheel well and it took about £22 of fuel, when hot the lpg system run at 70mph at about 10 pence per mile. That was very cheap on long distance drives, I did a 110 mile round trip for £9.58 or something like that and that was motorway driving.

Anyway the fuel gauge is now showing black on use of the vehicle. I will have to get used to keeping a tank 1/4 as minimum for peace of mind.

Edited by IAmTheWalrus on Thursday 30th December 18:59

IAmTheWalrus

Original Poster:

1,049 posts

51 months

Tuesday 25th January 2022
quotequote all
IAmTheWalrus said:
Well thank you Davie,

The extra couple of litres being in the tank would make sense.

I am indeed trying to do it old school, I filled with £104 of diesel and reset the trip computer.
OK first set of results in. Filled up spent £105.27 on same shell v power 65.02 litres and the trip computer says 519.6

65.02 litres is 14.3 imperial gallons, so 519.6 / 14.3 = 36. 33mpg

Interesting. Mostly was 50mph highway though these are short journeys.

Edited by IAmTheWalrus on Wednesday 26th January 12:55