Strange Mileage on computer - help.

[NumberoftheBeast]

I know I am fooling myself here, but I put V-Power in twice to three times a week in at £20 a go. Light to light mileage depends, but with easy driving, this mileage can sometimes exceed 70 miles.

I do, however, have a slight problem as the estimated fuel range indicator seems to be playing tricks on me. Quite frankly, it's doing my nut in...

Sometimes, I will put 20 quid in from empty (let's say the range says 5 miles upon adding fuel) and once re-fuelled, the indicacator may say I would get around 40-50 miles of driving. Upon getting onto a steady motorway 70 and putting cruise control on, this number may almost double. I suppose this is fine...

However, every so often, I have this issue where I will put 20 quid in and the estimated range will say anything inbetween 15 and 25 miles. of course, this is low, but what's worse, the petrol light is still on, the needle is in the red, literally right to the far left (as far as can be) and then literally within a few miles, I am on zero and having to fill up again.

The above happened last night/today and it's really odd and irritating, as I don't want to get caught out without petrol, when I should safe in the knowledge that I have just put 20 quid in. Twenty quid of petrol is a good twenty litres... how can the computer say I am literally empty???

I got in last night and I supposedly had 25 miles of fuel left (the petrol light had just come on). This morning, I fired her up to go out and all of a sudden, I was on zero miles and after a 20 quid top-up, I was only on 15 miles, which went down to 5 after a 5 mile motorway journey.

Can anyone help? Like I say, it's a bit baffling and although I know 20 quid at a time is kidding myself as I am putting fuel in more often, I don't think that 20 quid should give me 5 miles.

Any help/advice/suggestions would be truly appreciated!
Thanks

David

[BigMo]

I suspect this has summat to with the "mini" fuel reservoir that can be found located on the fuel line from the tank to the engine. I'm not sure as to it's capacity but certainly can play tricks with the fuel guage. Dude, you really got stop this £20 thing.

[Fen]

I had exactly the same thing when I shoved in £20 of Texaco super as I couldn't get to a Shell, then the next day I had 5 miles left. To be honest I find every time I get in the car after parking it overnight the range has dropped a lot compared with what it was when I left it. My BMW did the same, but on the BM it would come back up at roughly the rate the miles go on so if for example it said 25miles it would still show mid-20's (BMW one goes in 1mile steps not 5 miles) after I'd driven 25miles. The 6 will typically start with 5 miles to go if it was down to sub-40 the day before and then acts as if that's correct and drops to zero quickly. Alternatively I can park it with 1/4 tank and the next morning the light is on and it's saying 35miles to go.

I know Harry Metcalf said the same about his long term 6 that he ran for Evo so I just put it down to an annoying quirk.

The solution is to put more than £20 in at a time though! I brim mine every fill provided I'm at a Shell (don't get Tesco 99 in the sticks yet) and that's much more satisfactory.

[Kev.S]

Isn't this down to the way it's measured. Computer works out how many miles you can do at current consumption. Cold engine on start-up = 4 mpg. Warm engine when turning off = 16-25 mpg. £20 worth will give you less than 20 miles when cold.

[imolas4uk]

it could have a fuel tank sender fault (it has three) check the measured values in the dash with vag com

[NumberoftheBeast]

Thanks guys.

I think the solution must be to start filling up once a week as oppose to 2/3 times a week. I just like standing there all proud of myself filling up LOL.

Regarding checks via VAG com, I'd like to have mine on there to check out how the car is in general and, if possible, activate auto-locking upon driving off. Is there anyone local(ish) with it. I am in East Manchester.

Thanks again.

[el_ringo]

I find that the range and fuel gauge are both useless! Generally use the trip computer as a guide, 300 miles on that and I’m overdue a fill up!

[rjpatrick]

On the S6 I had the fuel sensor had a broken wire which would connect until it was about 1/4 full then suddenly report empty - (as usual Audi wanted to dismantle complete car and dashboard etc to look for it while emptying my wallet).

I dismantled the sender from the tank (quite tricky until you have seen one out) repaired and replaced worked fine for the next 60,000 miles.

Have done the same with the RS6 and found that the construction of the sender has fixed this potential problem so I think that it must be the Kev.S answer (massive thirst while warming up) - you could always carry a can in case it catches you out - in my experience trying to fill up in lane 3 is not recommended as a life enhancing activity though.

rjp

[Kev.S]

I find that the range and fuel gauge are both useless! Generally use the trip computer as a guide, 300 miles on that and I’m overdue a fill up!

I always fill my cars to brim and keep fuel/mileage records on a spreadsheet. The average mpg on my RS6 and S8 were all optimistic by an exact 10%. I also tested the speed on my RS6 using two different GPS and radar and an indicated 40 mph was actually 38 mph. Funnily enough, the S8's speedo is spot on.