As some of you may recall I have a 2001TT CPO that has been eating a lot of oil (~450 miles per quart in normal city driving conditions - no mods). The dealer has confirmed is currently running tests (leakdown and compression) but indicates everything is normal with the exception of sparkplugs looking particularly old. The 60k service was done at 56k and the car has now 69k - so here is my question:

Can the old sparkplugs be impacting oil consumption? If I recall correctly they need to be changed every 30k so a ~13kmiles sparkplug should still be ok.
Any other ideas of possible cause and tests suggested?
Thanks

 

Has the dealer confirmed that the oil consumption is 'actionable' under the CPO and PCNA will cover repairs?

If so, tell them to either fix it or replace the motor- it isn't your concern to do any more tests (ESPECIALLY on your dime)

Plugs cannot increase oil use, and after 13k at your level of burning oil they'd look like crap anyway.

 

The dealer has confirmed that a)the car is consuming more than the "maximum allowable" and b)has now opened a "case" with PCNA to get it solved. He indicated that the standard operating procedure is to run these tests (all paid by PCNA)to help determine the problem and fix. However, he has not said if the oil consumption alone will mean that it will be repaired (but of course I believe it must). Can you tell me how does burning oil make the sparkplugs look like crap?
Muker (a.k.a. Chronon)

 

No, but burning oil will destroy your plugs.

 

The problem is that oil is getting to the plugs to be burnt. Whether it gets burnt
well, or whether it fouls the plugs etc. is secondary to the fact that oil is either
getting past the valve guides or piston rings or both.

 

So if the dealer says that the issue is the plugs, that is BS. To make sure I get it - The issue is OIL getting to the plugs (from piston rings or valve guides) which will cause them to look like crap (but there is no way that bad plugs would impact oil consumption).

 

I have another question - does it make sense for the leakdown and compression tests to have good results if obviously oil is getting past the valve guides and/or piston rings?

 

I'd venture the guess that oil consumption- isn't going to always show on a compression test.

Some back of the napkin math: 1 qt per 500 miles... so at 50 mph thats 10 hrs.... at 3000rpm that is 1.8 million revolutins in 10 hrs. How much oil is lost per revolution? 6 cylinders, 10million cylinder/piston cycles.

How much oil do you need to loose on one cycle to have a noticeable effect on oil consumption? 10 million 'chances' to loose 1000ml of oil... or 0.0001ml per operation.

(Did I get this right??)

Glad they've opened the case...

Tell the dealer to write down, on a work order, HOW the bad plugs increase the oil consumption... especially if they are asking you to pay for a plug change. ("Well the plugs are pretty bad, which might be causing the high consumption- we recommned you change them bit since this is maintenance it would not be covered under warranty"... so have they explain their 'theory' in writing- I expect it wouldn't go any further.)

GL

A

 

They have done both tests compression and leakdown. While I have not seen the printout, dealer indicated results were normal for both. However, he indicated sparkplugs looked like "they were the originals..." (ie very bad shape). 60k service was done 13k miles ago. All these test are being done under warranty but what I want is a solution!

 

how do the plugs look? If they are not black and the motor is still buring oil it would be a bad exhaust seal or guide, this will still burn oil but it will all go out the exhaust and not really effect the plug.

 

Several comments here:

First, in order to do the leakdown test, they had to remove all of the plugs. For an extra $50 they could have replaced them with new ones when they put them back. If they "looked like crap" at the time, and they didn't replace them, that was pretty negligent. The cost of getting to the plugs is way more than the parts cost for the plugs themselves.

Second, I can't see how dirty plugs could affect oil consumption. Burning oil will make plugs look ugly.

Third, the oil has to be going somewhere. Could it be leaking through the turbos? Do you get blue smoke at startup?

jon

 

The plugs looked very black (but not greasy) which was surprising since they were changed at 56k mi as part of the 60k service. The dealer still had the car on a lift and all 6 spark plugs connected to the black cables (ignition coils?) He had assembled the car yet (or replaced the spark plugs) since he was waiting for word from PCNA on what to do next. On the leakdown test he said all cylinders were less than 2% which is obviously very good. He said that given the compression and leakdown tests were all fine that PCNA may just indicate to replace the plugs and call it a day ---BUT obviously there is something wrong here with the engine. When asked to explain how would it be possible for the spark plugs tobe in such bad shape he mentioned it was possible that the dealer that did the 60k service "forgot" to replace them. I guess everything is possible right????? Really hope PCNA does the right thing

 

The question isn't 'how can the plugs look so bad'

The question is "how will replacing plugs reduce oil consumption?"

Is the argument the plugs are bad, the engine is rich and this is causing fuel wash? Does the oil show signs of fuel contamination? Is there anything suspect with the fuel trim numbers?

 

ard - YES - I think this is what the dealer tried to explain me as an hypothesis for new plugs as a solution (fuel getting into the oil) but honestly at that point I couldnt follow. The only thing that thought of answering back was "ok if there's fuel in the oil, why dont we test the oil" but he gave some vague answer that fuel goes to the top and evaporates so it wouldnt show up at significant levels in an oil test. What are the fuel trim numbers?