High Oil Consumption!!

[Himbo]

Hi all,
I have had my B6 S4 Avant for 3 months now and I love the car but the oil consumption is way too high. The owners manual states 1 litre for every 1200 miles but I am using 1 litre every 300 miles round town or 200 miles on the motorway (higher rpm)!

There is nothing dripping from under the car and there is no blue smoke, although if I blip the throttle there is more black soot coming from the left hand tail-pipe. It seems to be burning it through the left hand bank as all the plugs in that side were really coated up to the point where I had a misfire. The plugs in the right hand bank are perfect.

Any one got any clue? The engine has done 102K. If it was wear, you would expect the right hand bank to be similar. All four plugs in the left hand bank were coated the same. There is no abnormal noises coming from the engine, the power seems ok and i'm getting upto 26mpg round town!

I have yet to do a compression test. Is it most likely an internal problem or could it be something to do with the recirculation system?

Mark.

[no_RS]

Is the car on long life servicing, if it is suggest you change to fixed servicing and stop using the long life oil. The oil is very thin and I believe this contributes to high consumption.

[xyber]

As above.

Mine used to fly through oil when I got it. Swapped to Castrol Edge and it hardly uses a drop

[Himbo]

Not sure if it was on longlife or not. I intend to service it myself. In the 3 months I have had it, I have had to top the oil up with 9 litres. I used Motul 5w30 VW spec oil (504, 507) from Opie Oils. It does specify a drain interval of 10,000 miles. Is this long life oil?
Also I have just bought a 20L drum of Quantum longlife 3 from VW's trade outlet, bargain at £88. But from what you are saying this will go down quick too?

[BlingBling]

The fixed interval oil is 5w 40, VW spec 502. Change to this grade of oil and you should see an improvement. Worse case scenario is scored liners, something that S4's can suffer from.

[nihc]

Hi,

You say you get black smoke when you floor it from one bank. Black soot would normally indicate an over rich mixture.
But from one bank.

When you say the plugs were coated up - was that with petrol, oil or soot?

If it's soot then your lambda sensors on that bank are near failing. If it's petrol, then you have a misfire ( should show on MIL). If it's oil, then either, you haven't changed it for a while, it's diluted with petrol, or you have a big wear problem just on one side - not really a possibility.

Have you had a look at your "long term fuel trims" on Vag-Com? It's block 32. They will tell you a lot about what's going on with the fueling on each bank.

Chris.

[Himbo]

Cheers Chris for the info.

The plugs on the left hand bank were coated with a hard crusty material. The coating was about a millimeter thick, this caused one of the plugs to short and gave me a missfire. The coating was not wet. I wonder if it could be the lambda on that side, but that shouldn't give me the high oil consumption should it?

Could it be the PCV valve not functioning correctly, ie. not draining the oil back to the sump and throwing it all into the inlet? The plug that was missfireing is the one closest to the PCV connection on the inlet manifold.

I don't have the proper Vag-com lead, just a cheap one off ebay. So I can't access all data.

[xyber]

Cheers Chris for the info.

The plugs on the left hand bank were coated with a hard crusty material. The coating was about a millimeter thick, this caused one of the plugs to short and gave me a missfire. The coating was not wet. I wonder if it could be the lambda on that side, but that shouldn't give me the high oil consumption should it?

Could it be the PCV valve not functioning correctly, ie. not draining the oil back to the sump and throwing it all into the inlet? The plug that was missfireing is the one closest to the PCV connection on the inlet manifold.

I don't have the proper Vag-com lead, just a cheap one off ebay. So I can't access all data.

what colour was the crusty stuff, White and abit like traces of cement?

[Himbo]

Cheers Chris for the info.

The plugs on the left hand bank were coated with a hard crusty material. The coating was about a millimeter thick, this caused one of the plugs to short and gave me a missfire. The coating was not wet. I wonder if it could be the lambda on that side, but that shouldn't give me the high oil consumption should it?

Could it be the PCV valve not functioning correctly, ie. not draining the oil back to the sump and throwing it all into the inlet? The plug that was missfireing is the one closest to the PCV connection on the inlet manifold.

I don't have the proper Vag-com lead, just a cheap one off ebay. So I can't access all data.

what colour was the crusty stuff, White and abit like traces of cement?

Yeh, thats sound about right. It wasn't jet black. It wouldn't wire brush off I had to scrape it off with a knife then wire brush them.

[xyber]

You may have a small air leak on the inlet manifold or something else causing it to run slightly lean. Either the bolts need torquing up, the gasket is leaking or maybe slightly warped.

I recently changed my plugs and had the same and a bit of googling pointed to this. I'm gonna plug it into vcds at the weekend and see if it's showing anything, like lambda values fluctuating or something

[nihc]

Hi,

Try taking the oil filler cap off and give it a smell. Does it smell of petrol?

Chris.

[nihc]

Forgot to mention that looking at the fuel trims is the way to go.
Does the vag-com cable you have work at all? If so, go to the ""Engine" control module and select "Measuring Blocks" and type in 032 and see what you get.

Chris.

[Himbo]

Right, I've done a compression test on each cylinder;

Drivers side (front to back) 155, 160, 156, 159 psi.
Passenger side (front to back) 166, 160, 180, 180 psi.

It is the passenger side that has the coated plugs yet the compression is better in that side. Not sure why the back two are 20psi above the rest, maybe the rings are coke'd up. Either way, it does'nt look like I have broken rings or buggered valves.

I have taken the breather pipes off and all are clear. The pressure control valve at the back of the throttle body had a shity diaphram, so I've cleaned it and put it back together.

The oil does'nt smell as though there is any petrol in it. I havent been able to view the fuel trims yet. My next step is to fill it with 5w40 Castrol Edge and monitor it for a month or two.

Anyone know what the compression values should be? The engine has done 104K?