4.2 V8 Oil Usage Problem
 

Hi Folks,
I am new to this Forum so hope am presenting in the right place.
I have a 1999 Audi A8 with a 4.2Ltr Petrol Engine. I bought this about 18months ago. It is a genuine low mileage (about 60K). It is very smooth and averages about 28 MPG. However it has always been very thirsty on oil. I installed a catch can in the engine scavenging system but it collected no oil.
Today on removing spark plugs I find the left hand bank plugs are sooted up really badly. So oil is clearly getting into all the left hand bank of cylinders.
Has any one had this problem or have any ideas as to the cause.

That sounds like excessive ring wear...
 

… except that it is not uniform. No such deposits on the right? Do you see any bluish smoke when driving?? Is one side of the exhaust finishers more sooty than the other? How about start-up?

Hi, this heavy usage of oil was known when I purchased, previous owner had it compression tested which was reported as OK, I need to test myself, however with engine running on tickover with dipstick removed the engine is lightly sucking in air at dipstick suggesting rings OK, definitely not blowing out.
Start up and driving is as smooth as silk. Yes there is smoke from one exhaust and on a long run black oily carbon bits on bumper above exhaust. Its not doing much more than a 100 miles on a pint of oil. The plugs on the left hand bank are sooted up more than I have seen on any engine in years and that includes two stroke motors. Right hand bank are acceptable, if the economy wasn't so good I would think running very slightly rich which I am sure it isn't so there may be a slight oil burn on right but nothing of interest.
I wondered if the oil may not be draining down on left hand bank creating a bad leak down on the valves. Of course the valve seals would have to be shot as well. It would seem the car has always run on a 5-30 synthetic oil and at present is running on Shell Helix 5-30 Synthetic.
This car is a genuine low mileage vehicle which was regularly maintained by the main Agent for Audi and I have all those records. I note that others have reported this engine uses a bit of oil though not as bad as mine so I wondered if there was an intrinsic problem with this engine.

Hi, did you resolve your issue? Ive got the same problem!?! Would appreciate any advice. Cheers

Hi, No I haven't been able to solve the problem. I have tried the main Dealer for a solution and chocolate teapot is the kindest thing I can say about them. As I said earlier there is a slight vacuum being pulled when engine is running (detected at dipstick ), so I suspected oil was being sucked out of the scavenging system, so I inserted a collection tank in that system. to my surprise it collected hardly anything so its not that. As there is no blow by, believe rings are OK. I suspect oil is being drawn down the valve stems and wonder if the oil drain down from the top of the engine is adequate. The plastic oil shields on the valve stems are probably brittle and need changing. As my mileage on this vehicle is low and it runs fine I decided to live with it.
I was worried it might fail emissions because of the problem so I always use a low ash oil (withC3 on oil spec label) and so far have had no issues with emission test also do not now have black specks on rear bumper. Can only suggest you use a high spec oil and don't be tempted to use a thicker oil because that didn't help and may impede oil drain down.
Has your car always had this problem? Finally everyone I have spoken to says this series of engines do use a fair bit of oil.

Thanks for the reply/update, what do you mean by "wonder if oil drain down from the top of the engine is adequate", you think something could be blocked? How about the oil check valves in the valley pan? Think this could be worth replacing?

Hi, one of the reasons I wondered if the oil drains down from the top of the engine is adequate was I noticed that when the engine is running there is quite a drop in the oil as measured on the dipstick compared with the check when engine is not running. This is quite normal as obviously oil is pumped into the engine when running but it seemed a bit more than I was expecting, unfortunately only the designers would know what is normal.

Another line of enquiry that might help, I wondered if anyone on this site might know what, if any, alterations were made to this Engine by the manufactures on its later versions that might alleviate this problem. With particular reference to the lubrication system and the vacuum system.