Crazy fuel consumption - what can it be?

[spurtle]

Check the lambda trims? Faulty lambdas don't always throw a code but they can play havoc with the mix. Does it smell like it's running rich?

[el_ringo]

I'm pretty sure people have had lots of issues with the non OEM spark plugs.

[s4bandit]

what's a full tank cost ? i only fill up to £40 so not to get sick of the fuel prices rising ..lol and have been getting 100 miles if using vpower and 130 miles if using 95 ron.
after reading this post that sounds low ? the car runs perfect, accelerates like an airplane and doesnt feel like its running wrong though ?

[ecain63]

Why are you using 95? These cars don't like anything less than 97.

[s4bandit]

had to use it one day a couple of weeks ago when couldnt get 99 and got 30% more miles with no reduction in power, so used it again to double check, same result. currently trying to find out how and why this is happening on another post...http://www.rs246.com/index.php?name=PNp ... ic&t=86656

[Shoppinit]

I'm thinking that the oil from the K&N have killed the MAFs. Can you get a vagcom on it and see what the airflow g/s readings are for the MAFs?

Also the RS6 is know to pop the fuel pump gasket at the tank junction and leak fuel, but then you'd get the unmistakable smell when you park it up.

[Shoppinit]

you'd get the unmistakable smell when you park it up.

And I'm not talking about the one coming from your passenger's underpants

[jamesthecat]

cant see it being the plugs or filter as I'm running the same as you and mine has stayed the same i also had a snap-on camera and had a look inside the cylinders when plugs were out and had a light brown sheen on the top of the piston heads everyone of them were the same,cant even tell the difference between the 95-98 Ron petrol sounds the same when i put my foot down no pinking just thrust

[kaisersolsay]

I've used 95 shell a number of times (local garage stopped selling V Power) and she ran fine. In fact she manages pretty low 1/4 mile times on it.

I've just driven down from Perthshire to Centre Parcs at Penrith and on the M74 sitting at 70mph with full boot, 2 kids + 2 adults and 2 bikes on a boot rack I managed 28mpg. This is running Tesco 99 Momentum.

Just shows you can get semi decent economy out for them when you feel in the mood.

[Shoppinit]

Says in the manual to use 95 only in emergency and not to use full throttle if you do. I have seen my car pulling the ignition timing almost to the upper limit on 98 octane on the rollers - I dread to think what the ECU is doing to try to protect the engine on 95 octane.

[kaisersolsay]

Touche. I don't make a habit of using 95, and now ensure that I keep her topped up with 99 Tesco juice. Its worth keeping her with 1/2 tank max what with the huge capacity. The 1/2 tank weight saving around town and short journey's is got to be worth 5-8mpg! Make sure tyres are correctly inflated also. I had a 530d a couple of years ago and on the way home from the dealers only saw 25mpg! I had a look when I got home and realised that all 4 tyres were sitting with 10-15psi! Not great for a main dealer, but easy to sort. With a little more air she was averaging 43mpg.

[drybeer]

I've used 95 shell a number of times (local garage stopped selling V Power) and she ran fine. In fact she manages pretty low 1/4 mile times on it.

I've just driven down from Perthshire to Centre Parcs at Penrith and on the M74 sitting at 70mph with full boot, 2 kids + 2 adults and 2 bikes on a boot rack I managed 28mpg. This is running Tesco 99 Momentum.

Just shows you can get semi decent economy out for them when you feel in the mood.

Are you sure?

This is almost exactly what I dod on vacation to France over summer, full car and two bikes. Averaged 22 ish mpg. Can get 28 if car much more streamlined, i.e. not bikes or roof rack.

Was your result off the DIS or a fill - fill test?

[kaisersolsay]

DIS mate. I too drove to France earlier this year (Perth - Lyon) and averaged 25-26mpg with a full boot, 3 adults and 2 kids. Used 99 to Dover and then French 97 till we got back over the channel. Paris - Lyon on the quiet toll roads I sat at a ton for nearly 150km and still averaged 20mpg on the nose. No bikes this time. And that's a tank fill calc. Trans-european travelling sure highlights how much fuel these beast drink! You fill up and 3 hours later you need to fill up again!

[paul_23]

If the MAFs are shot then log them and the fuel trim in VAGCOM - there are limits and if it is trimming it due to being too rich then it will throw a fault code like
17546 - Fuel Trim: Bank 2 (Add): System too Lean
P1138 - 001 - Upper Limit Exceeded
17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 001 - Upper Limit Exceeded
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 001 - Upper Limit Exceeded - Intermittent
17538 - Fuel Trim: Bank 2 (Mult): System too Lean
P1130 - 001 - Upper Limit Exceeded - Intermittent

Log blocks 1-2 and 32 (I think) and this will show the lambda values too.
If it is not showing anything peculiar then it wont be the plugs. In which case it could be a leak - check when switched off and idling at start up (cold) at the tank and trace fuel lines back to fuel filter and into engine bay. For such low economy it must be a fair sized leak but if it is near the engine or exhaust it will evaporate quickly so do it when stone cold.

[PaulRS6]

I had a situation a little while back where my car was drinking more furiously than normal and it may be, given that yours has just been serviced that this explains it. The stealer that did the service for me didn't re-align the one of the air filter casings correctly so air was getting in around the sides of it. This made the MAF readings saturate and it just kept trying to chase the air with more fuel. I was seeing about 50 miles per quarter tank. One thing that gave it away was that I could hear the turbos spooling up where I couldn't previously.

Just my 2p, HTH.