Weird fuel gauge behaviour

Chat about your 6R/6C model Polos here!
luuts
New
Posts: 4
Joined: Wed Sep 23, 2015 8:54 pm
Drives: VW Polo R Line 110ps

Weird fuel gauge behaviour

Post by luuts »

So a funny thing happened tonight on my usual drive from the west of Scotland to Manchester.
I'd filled my Polo (65 plate R-Line 110ps) and noticed that my fuel gauge didn't shift from full for about 200 miles. Then went down a tiny bit. Usually I'd see the needle start to move after about 70 or so miles so this was really bizarre.

So after 234 miles, with an average mpg of 52.9 (which is fairly average for this journey usually),the fuel gauge has moved only 1 and a half sections and my range was still 395 miles, which seem pretty crazy. Usually after this drive, my fuel gauge would be somewhere between 1/2 and 2/3 full.
Anyone ever seen something like this before? Any ideas how to fix it?

Image
Image
Last edited by luuts on Sun Apr 17, 2016 10:05 pm, edited 1 time in total.
tomtoon2015
Bronze Member
Posts: 161
Joined: Mon Jan 12, 2015 10:32 pm
Drives: 2015 blueGT

Re: Weird fuel gauge behaviour

Post by tomtoon2015 »

Jees, that's better than the BGT which is meant to be an eco car haha. That does seem weird that both the gauge and range indicator seem to be wrong.. Perhaps check the manual to see if there's a reset for it? Not heard of it myself :)
luuts
New
Posts: 4
Joined: Wed Sep 23, 2015 8:54 pm
Drives: VW Polo R Line 110ps

Re: Weird fuel gauge behaviour

Post by luuts »

It is weird isn't it! Can't find any mention of resetting it anywhere, so I guess it's back to the garage to get it looked at.
I know that fuel gauges aren't particularly accurate (I used to have a VW up! that could go about 110 miles before the needle moved! And that was considered normal) but I'd like some confidence I'm not gonna run out of fuel randomly without realising it. :shock:
RUM4MO
Bling Bling Diamond Member
Posts: 5859
Joined: Sat Dec 30, 2006 9:12 pm
Drives: B8 S4 & 6R/6C1 1.2TSI 110
Location: Mid Lothian

Re: Weird fuel gauge behaviour

Post by RUM4MO »

Are you sure that you have not just "force filled" the tank beyond the usual first or second click? I've done that a few times with my wife's August 2015 Polo 1.2TSI 110PS SEL - in fact I think that the current tank of fuel is still at "full" after quite a lot of miles - I don't normally deliberately over fill the tank, but sometimes that is what happens and will be reflected in the miles this fill will last.

Remember the "trip" miles being displayed can be false as it needs to be reset manually.
luuts
New
Posts: 4
Joined: Wed Sep 23, 2015 8:54 pm
Drives: VW Polo R Line 110ps

Re: Weird fuel gauge behaviour

Post by luuts »

RUM4MO wrote:Are you sure that you have not just "force filled" the tank beyond the usual first or second click? I've done that a few times with my wife's August 2015 Polo 1.2TSI 110PS SEL - in fact I think that the current tank of fuel is still at "full" after quite a lot of miles - I don't normally deliberately over fill the tank, but sometimes that is what happens and will be reflected in the miles this fill will last.

Remember the "trip" miles being displayed can be false as it needs to be reset manually.
Yeah, I guess it could have been down to overfilling if it were a small difference. But to do 200 miles and it not move at all, surely there'd have to be a heck of a lot of extra fuel between first click and whatever I'd filled it to?
I'm only really worried because it was on a trip that I do fortnightly, so I'm used to when and where the needle starts to go down.

RUM4MO, how much extra fuel can you get in your wife's Polo by force filling? I've never tried it, at least not deliberately...
RUM4MO
Bling Bling Diamond Member
Posts: 5859
Joined: Sat Dec 30, 2006 9:12 pm
Drives: B8 S4 & 6R/6C1 1.2TSI 110
Location: Mid Lothian

Re: Weird fuel gauge behaviour

Post by RUM4MO »

Humm, 200 miles at 60MPG, is still roughly 15 litres!

I get the impression that with some filling station nozzles, you can end up "under" filling easily by that amount, which can be annoying, for "over" filling, and this is just a guess, I'd be thinking that 5>10 litres is easily possible, so that is getting up to where you could be if you forced the last 5 litres in by venting.

If I were to make a generalised statement wrt VAG fuelling, the first "half" of the gauge travel is normally optimistic and the second "half" is frighteningly pessimistic! So, over a full tank's load of fuel at a constant MPG, the first "half" travel would be reached after 65>70% of the actual range, so the second "half" of the gauge travel would be used over the remaining 30>35% of the range - well maybe that is exaggerating a bit!
tomtoon2015
Bronze Member
Posts: 161
Joined: Mon Jan 12, 2015 10:32 pm
Drives: 2015 blueGT

Re: Weird fuel gauge behaviour

Post by tomtoon2015 »

RUM4MO wrote:Humm, 200 miles at 60MPG, is still roughly 15 litres!

I get the impression that with some filling station nozzles, you can end up "under" filling easily by that amount, which can be annoying, for "over" filling, and this is just a guess, I'd be thinking that 5>10 litres is easily possible, so that is getting up to where you could be if you forced the last 5 litres in by venting.

If I were to make a generalised statement wrt VAG fuelling, the first "half" of the gauge travel is normally optimistic and the second "half" is frighteningly pessimistic! So, over a full tank's load of fuel at a constant MPG, the first "half" travel would be reached after 65>70% of the actual range, so the second "half" of the gauge travel would be used over the remaining 30>35% of the range - well maybe that is exaggerating a bit!
I agree with that statement.. My moves after 50-60 then moves quickly to 1/4 tank used (normally 130/140 miles) then the last quarter of the tank I'll usually get 70-85.. Really stupid how they behave tbh lol
d7lan
New
Posts: 49
Joined: Sat Mar 05, 2016 3:29 pm
Drives: Awaiting delivery of 6C GTI 5dr
Location: Glasgow

Re: Weird fuel gauge behaviour

Post by d7lan »

I used to be able to squeeze an additional 5 litres (i.e. just over a gallon) into my 2011 Seat Ibiza. I would guess the Polo is similar.

Its a small overflow tank, which can be filled if you insert the pump nozzle a particular way. The end result is an extra 50 miles on a full tank, and the gauge showing full for longer

Sent from my SM-G920F using Tapatalk
RUM4MO
Bling Bling Diamond Member
Posts: 5859
Joined: Sat Dec 30, 2006 9:12 pm
Drives: B8 S4 & 6R/6C1 1.2TSI 110
Location: Mid Lothian

Re: Weird fuel gauge behaviour

Post by RUM4MO »

d7lan, it is not a separate overflow tank, it is the top of the fuel tank that is meant to be left free of fuel initially so that any thermal expansion moves the fuel level up into there and not out the vent, or in the case of modern cars - into the pipe leading to the EVAP canister - or even into the EVAP canister, which can be problematic.
luuts
New
Posts: 4
Joined: Wed Sep 23, 2015 8:54 pm
Drives: VW Polo R Line 110ps

Re: Weird fuel gauge behaviour

Post by luuts »

Thanks for the replies guys!
The original reason I was worried that my fuel gauge was busted was because I had recently had my dash instrument cluster replaced due to the issue where the trip button gets stuck in, which seems pretty common! Had the car looked at yesterday by VW and they couldn't find anything wrong with it, so I guess either my car is amazing and suddenly gained magic fuel saving abilities, or I/the fuel pump overfilled my car :oops: .
RUM4MO
Bling Bling Diamond Member
Posts: 5859
Joined: Sat Dec 30, 2006 9:12 pm
Drives: B8 S4 & 6R/6C1 1.2TSI 110
Location: Mid Lothian

Re: Weird fuel gauge behaviour

Post by RUM4MO »

Fair enough, I too might have been a bit concerned if other issues just happened after this repair, hopefully over the span of the next few tank fills you will get closer to what is happening and either trust the car or get it in for sorting properly.
d7lan
New
Posts: 49
Joined: Sat Mar 05, 2016 3:29 pm
Drives: Awaiting delivery of 6C GTI 5dr
Location: Glasgow

Re: RE: Re: Weird fuel gauge behaviour

Post by d7lan »

RUM4MO wrote:d7lan, it is not a separate overflow tank, it is the top of the fuel tank that is meant to be left free of fuel initially so that any thermal expansion moves the fuel level up into there and not out the vent, or in the case of modern cars - into the pipe leading to the EVAP canister - or even into the EVAP canister, which can be problematic.
You learn something new every day! I had read that on the Seat forum. Should know not to trust everything on the internet. Cheers

Sent from my SM-G920F using Tapatalk
d-ash
Getting There!
Posts: 87
Joined: Mon Dec 12, 2016 11:16 am
Drives: 6C 2016 R-Line 1.2 90PS - Blue Silk
Location: Darlington

Re: Weird fuel gauge behaviour

Post by d-ash »

Explains how I got 51 litres into mine on one occasion
RUM4MO
Bling Bling Diamond Member
Posts: 5859
Joined: Sat Dec 30, 2006 9:12 pm
Drives: B8 S4 & 6R/6C1 1.2TSI 110
Location: Mid Lothian

Re: Weird fuel gauge behaviour

Post by RUM4MO »

51 litres, 51 litres? I ran my wife's August 2015 Polo 1.2TSI 110PS SEL down to about 20 miles range on Sunday night (518 miles) and managed to force 41 litres into it, that is the most (equal) that I have ever stuffed into it - and I know that I should have stopped at 39 litres!!
d-ash
Getting There!
Posts: 87
Joined: Mon Dec 12, 2016 11:16 am
Drives: 6C 2016 R-Line 1.2 90PS - Blue Silk
Location: Darlington

Re: Weird fuel gauge behaviour

Post by d-ash »

Official tank capacity is 45 litres
Post Reply