A6 4.2 Oil Consumption

[andiamo27]

Have a 2000 Audi A6 4.2 with 70k miles.

Recently, oil consumption has increase to approx. 1 qt. (AMS Oil Synthetic)per 700 miles.

There are no external oil leaks visible, although the dealer convinced me to reseal the front cam chain covers ($1,700.00)as they were convinced that the oil was leaking externally. There is no evidence of any external oil leaks (Have been parking the car over 24 inch wide Kraft Paper, no leaks noted).

After repairs the oil consumption continues at what I consider an unacceptable rate. Prior to this dramatic increase in oil consumption no oil was added between changes (3,000 mile intervals).

Cannot detect any oil coming out of the exhaust, even after letting the car sit overnight, there is no "VISIBLE" oil smoke emitted from the exhaust at anytime especially on start. (I suspected valve guide oil seals, or worse).

Please advise if anyone has experienced similar oil consumption issues with the Audi A6 4.2.

Of course Audi Service is claiming that 700 miles per quart of oil is acceptable.

[Sven]

Firstly, welcome to TSN!

There are other known instances of oil consumption on the 4.2. If there's no evidence of leakage I wouldn't bother with spending $1700,- on sealing something that's probably just fine.

Check coolant and oil for evidence of mixing. If not, I'd live with it. It's not that excessive, and fixing it would almost definitely be costly, and ask for some rebuilding of the engine. (may be cylinder walls or piston rings).

So unless it's covered by warranty...

HTH

[andiamo27]

Thank you for the response. There is no evidence of oil mixing with the coolant. Also, have already spent the $1,700.00 for resealing the cam chain covers.

I did have one thought that might have contributed to this condition. The check engine light came on and the dealer could not take the car for service for 2-3 weeks (due to new owner and location change). Finally bought the VAG-COM cable and ran a diagnotic.

We found two items wrong after the scan:

1. Several Vacuum Hoses had deteriorated and were leaking due to heat.

2. Found a Lean Fuel condition on Bank 1 and 2 that was due to a faulty Mass Air Flow Sensor. The car may have been driven approx. 1,000 miles with this condition. The Mass Air Flow Sensor was replaced, however, the check engine light came back on after the Re-Seal of the Cam Chain Covers and it appears the recently replace Mass Air Flow Sensor is at fault once again. My point is, could this lean condition have cause Cylinder Wall Damage. We have a 4mm Borescope at our Hangar, I guess the next step is to see if the Cylinder Walls are damaged.

[Sven]

Ah, you do have all the right toys I see...

Not sure whether the lean burn alone could cause damage to the cylinder walls that soon. However, if the oil pressure has been low, that could be a cause. However, that should have produced a separate red warning light IMO. (Check engine was the orange one, and not flashing?).

The scope sounds like a good idea. Allegedly, there also has been an issue with the cylinder wall lining at some point, which was later changed. (This 'issue' is debated though).

However, my engine was replaced due to scratches in the cylinder walls. I had just bought the car, and on the first trip (I felt it was a good excuse to see Prague and test the car) it consumed a staggering amount of €20 a litre long life oil (11 litres over 3000 km).

The garage owner (it was his private car) said he "never noticed anything before", "I must have been driving very fast" (duh!), and whatever else he could come up with. It turned quite nasty for a while, but in the end I got a new engine, with a 2k contribution on my part. It was either that or let them take the engine apart to replace the lower block at no cost. Well... needless to say I chose the new engine.

What caused it remains a mystery, but some say it was the poor cylinder lining. Strange thing was the car was surveyed by an independent organization, prior to purchase, and they found nothing. It didn't smoke, the exhaust and rear end didn't get greasy, it didn't leak, nothing. The oil just disappeared.

Obviously, your engine doesn't nearly consume that much oil, but since you have the equipment, it's worth a look.

What's strange is that the MAF is faulty yet again. Could they have damaged it perhaps? No over-oiled aftermarket air filter? No leaks in the air intake (after the MAF)? I have noticed many weird things happen if the MAF is bypassed and it doesn't read the correct airflow. Even ABS and ESP lights came on....

I presume the vacuum hoses have all been replaced?

I'll notify my good friend Paul, the founder of www.audipages.com (very useful site, based on the 8, but may be interesting for any 4.2 owner), to see what he thinks of this.

Keep us posted of your findings!

[PaulW]

Some Audi engines consume oil, I have a 32 valve 4.2 A8 that consumes about 1 quart of oil every 7,500 miles. Pretty much goes from the top of the add level to the bottom of the add level.

I have 117,000 miles on the car.

All my previous Audi's burned more oil as they got older, but never at a rate of 1 qt/700 miles.

Audi does state that up to 1 qt/1,000 miles is not excessive.

I do not really have an answer for you, if you had an oil leak, you would see it if it was 0.5 qt/1500 miles. But you don't see anything.

I would monitor the situation.....maybe even do an oil change, run it for 3,000 -5,000 miles adding as required (and logging exactly how much goes in it) and then take a sample of the oil and send it out for analysis.

This might show you if there is any wear going on.....and could help you troubleshoot the problem.

pw

[richardd]

I also have an oil consumption problem with my 4.2 engine. The A8 has done about 90K miles and I noticed that the oil consumption was getting worse.

The car was under warrantee so my local Audi dealer replaced the engine block. Unfortunately this has not solved the problem .... the car continues to consume around 1 Litre of Oil every 450 miles.

The car is back with Audi at the moment. I will let you know what the find.

Richard

[grahamb]

Question: Where does all the oil go? Surely, if an engine consumes that quantity of oil in such a short space of time, theres either puddle of it on the floor under where the car is parked, or its being burnt with the fuel. In which case, wouldn't there be smoke from the exhaust? Any car that uses a litre of oil in a 450 miles must smoke like a chimney. Or do the catalytic convertors absorb the oil, thus preventing any smoke from exiting the exhaust.

I'm intrigued to know where its all going.

[Edd_W]

it has to be passing into the combustion chamber and then out through the exhaust. It is possible that the cats will reduce the prticulate emissions to a point where they are not visible because they will act like an after-burner and heat the smoke particles to such a point where they burn cleanly.

My guess is that trying a different grade oil may prove the theory. You could try a 15/w50 because that will be less prone to being drawn past the oil control rings. If this helps then short an new bottom end or a small over-bore and new pistons you are stuck with it. There is a small possibility that it could just be the valvle guide oil seals. These are cheap but nearly as much work to replace as a full engine re-build becuase the heads should come off. It is possible to replace the oil seals with the head on bu using a air line to pressurise the cylinder. If it works, you could chage them all in one afternoon. You just have to lift the cams out, then the followers and find a valve spring compressor which will crack the caps off without pushing the valve down too much. I made up one for doing passat/golf 8v heads years ago but I have never used on something like the V8. The theory is fine though.

[richardd]

The oil loss has got progressively worse, it was about 2 Ltrs per 500 miles a few weeks back, with a great deal of Blue Puff, especially when pulling away from stationary.

Audi have now decided to replace both the heads to see if this resolved the problem.... (it already has a new block!)