Severe oil burning: highly detailed post, need technical advice

Hi guys, So I am in need of your wisdom, as I am at the end of the road here with any and all ideas as to why I have extensive oil burning issues. The dealer has provided very little assistance and just says it can be anything. Below is a list of all the background, details, and testing to date. I hope that one of you uber techies can assist. 1. Car is a 2006 Cayman S 6 speed. 2. Burnt absolutely no oil from new till about 50k miles. All of sudden at 50k miles started to burn 1 quart per 600-800 miles. Heavy carbon deposit on rear bumper and tailpipes. 3. Oil changes intervals varied from 1 - 2 years with roughly 15-20k miles between oil changes, as per Porsche maintenance placard. Car was daily driven. 4. No previous technical issues with car aside from waterpump failure at roughly 45k miles. 5. I did some research and changed my AOS , as this seemed to be a common culprit in many cases. This had no impact on my oil burning consumption. 6. Had dealer do full inspection on car at ~60k miles. Dealer indicated that all cylinders were scoped with no scoring found. Cylinder 4 had minor oil pooling, but no cause could be determined. Plugs had light buildup of carbon. Pressure test done on cylinder 4 with loss of 6 PSI at 90PSI, vs cylinder 5 with loss of 5 PSI at 90 PSI. Crankcase and exhaust pressure all within specification. Dealer indicated they didn't know what was wrong and to just continue driving car. 7. Oil and filter sample results were sent for analysis around the same time. Oil was 18 month old and had 15.5k miles on it. Concerning results came back as follows. a. Aluminium 10 ppm. b. Chromium 3 ppm. c. Iron 51 ppm. d. Lead 11 ppm. e. Silicon 21 ppm. 7. Car recently, at 80k miles, started to surge a bit on startup and throw engine code P0421 (warm-up catalyst efficiency below threshold bank 1). I drove the car like this for a few days as it was completely drivable and I couldn't make it into the dealer. I then parked the car for 4 days, after which when I started the car it ran really rough, was misfiring, and threw codes P0302 (cylinder 2 misfire), P0421, P0431 (catalyst efficiency bank 2), P0300 (random misfire). The car was underivable and I towed it to the dealer. 8. Dealer found all 6 spark plugs completely black (carbon) and dry. Found oil pooling in cylinder 2, but not in other inspected cylinders. Further inspection found intake header and MAF covered in oil, which required cleaning as engine wasn't operating at higher RPMs. Plugs all replaced, oil changed, and oil cleaned from intake system. Dealer stated that they are unsure as to what caused this, and to keep on driving car. Please note that I recently replaced the plugs, so these fouled plugs only had 20k miles on them. I also replaced all the ignition coils about 4 months prior to this event. 9. I took the car home and it ran perfect, but oil is still burning. I actually always used Mobil 1 0W40 per Porsche spec, but after this last issue asked the dealer to switch it to Amsoil Euro Spec 5W40, as I heard a lot of guys stated it didn't have high consumption like Mobil 1 . I checked the oil level and it dropped 1 bar within 60 miles, so I am not sure I am having any different luck with a different oil type. 10. I then recently parked the car for another 6 days and started it without any issues. It ran fine with no hessitation or surging. I also re-rechecked the AOS by opening the engine oil cap and there is very little vacuum, so seems like AOS might be okay. I also noticed that if the car is parked for maybe 1 day, upon startup I get a plume of white smoke but it subsidies after a few minutes to a very small amount. I don't really know what to do next as the dealer thinks it might the piston rings, and feels that air intake system contamination could have been due to over pressurization of crankcase and sucked in by PCV valve . Dealer did not do any other tests or suggest any other course of action aside from what I mentioned. Dealer just says to keep on driving it like this, which obviously doesn't seem like a very reasonable statement. Unfortunately I only have one dealer in the city and can't get a second opinion aside from aftermarket shops. I was just thinking maybe I need to do a leak down test on each cylinder, as I can't come up with any other ideas. The other thing is that all 6 plugs are contaminated with carbon, but if I had a specific cylinder issue then wouldn't I just have that cylinder's plug contaminated? Also having heavy oil contamination in the intake system seems like maybe something else is causing all of this and then equal distributing oil contaminated air into all 6 cylinders? I would greatly appreciate any assistance. Regards, VadRad

hello, first things first... I wanted to stop reading at "Oil changes intervals varied from 1 - 2 years with roughly 15-20k miles between oil changes"... wow , just wow.. 15-20K between oil changes for several years and you are wondering why your car is burning oil.. wow did you plan on owning this car long term? Did you think it was OK for your new car to run 15-20K miles for 1-2 years without an oil change? If your response is, well I was just following Porsche Maint Placard, then we have nothing to talk about. 2ndly, I am confused at your apparent frustration at the dealer. They dont have some magical way of finding the reason for oil consumption. I am sure they would be happy to tear down the engine and charge you a few thousands in labor, I am guessing you dont want that? Also, how long has it been since you changed the AOS ? Have you ruled out its not AOS all over agin? Your options really are to keep driving the car till you can't, and replace the engine with a used one that was properly maintained. Leak down test may be beneficial in your situation.

Yea that is a long time for an oil change on these cars. I do mine every 3000k or 7 months. Perhaps it is a bad AOS ? I know it was changed but sometimes they are bad from the gecko. I would recommend taking the car to another shop for an evaluation. Sent from my SM-N910P using Tapatalk

First off, I'm no expert, but it does seem like it has to be something that would impact all cylinders, so a leaking AOS (despite the change) seems worth checking. Rather than change it I'd suggest the simple crankcase vacuum test - see Pelican site for method. Yeah, those oil change intervals seems a little long, despite meeting Porsche 's recommendation. It would have been really interesting to send a sample in for testing. I tend to change around 5k and Blackstone tells me to wait longer.

No bore scoring is geat news. While it's possible the rings on all 6 cylinders went simultaneously, the condition of all plugs certainly sounds like a common-cause problem, though there may be a separate issue in Cylinder 2. It certainly seems as though some of your missing oil is ending up in the intake. If not the AOS , though, I'm at a loss to speculate where else the problem may lie. AOS failure wouldn't explain oil in the MAF, though, that oily air would enter the intake downstream of the MAF. I wonder... it could be an issue in cylinder 2 causing extra blow-by into the block, which causes a higher volume of oily air (just vapor, not liquid) to pass through a perfectly functional AOS . Porsche recommended 20k oil change intervals for 987.1. Porsche specified this after nearly a decade of specifying 15k intervals for the very similar M96 engine. It's an engineering matter, not a religious one; you don't need to interject your own superstitions into it. Do either of you, or anyone else recommending ridiculously short oil change intervals, have any shred of data to support your belief that Porsche is lying and 3k or 5k oil change intervals is necessary?

I appreciate all the responses to date. As per the suggestions regarding AOS , I asked the dealer to inspect it as per Pelican parts article for vacuum, but dealer refused. Dealer indicated that they have no reason to suspect a malfunctioning AOS . I myself did the hand/cap vacuum test and didn't seem to notice any substantial vacuum at the oil filler cap when removing it. It seems like the AOS might be okay, but hard to say without a technical test. I am trying to focus this on the oil contaminated MAF. There was also some oil noticed pooling just upstream of the MAF within a low area of the tubing. I am mostly curious to figure out why I have oil in the air intake system, and why I have 6 carbon coated spark plugs . I have a hunch that maybe this has something to do with why I am burning so much oil, or maybe its just a byproduct of it. Does anyone feel this might have something to do with a failed PCV valve or CVS system of the crankcase? Any other ideas I can try? Thanks, VadRad

The described symptoms all seem to point squarely at the AOS ; burning oil, all plugs fouling, dirty MAS, CEL's for cats and probably O2's. Interestingly performance might seem OK when at WOT since intake vacuum would drop resulting in temporarily less oil being sucked in; at least until you backed off the throttle to shift or slow down. Is it possible that one of the AOS ' vacuum lines is also leaking, and thereby leading you astray with inaccurate results fro your crankcase vacuum test? Pelican article specifically recommends replacing one of the hoses as the same time... Finally, continuing to drive the car with its current oil consumption is greatly increasing the possibility of permanent damage to the cats. And according to Pedro's can even lead to hydraulic lockup of the engine. All bad.

AOS ! Do a leak down test if you know the person doing it knows how to, and understands the meaning of the values obtained, not always easy with a boxster engine. Personally I would rely on the compression test for simplicity given you have had a bore scope already. If the cylinders are giving approximate values then forget about the rings, unless you have run it dry of oil and just forgot to tell us about it??? The oil pooling described is hard to interrupt without knowing how much, time between the engine running and the inspection and the cars resting position/angle prior to being inspected. The flat 6 integrated dry sump design does allow oil to weep past the rings when stationary, and is not necessarily a cause for concern. But it is a question of degrees. At idle there should be a pretty substantial vacuum at the oil filler cap, it should want to suck the cap back into place as you rotate it off the threads because the AOS valve is open due to a lack of pressure differential between the intake manifold and the crankcase, that is until you open the cap. The cylinders want all the air they can get but the throttle valve is closed so it won’t let them get it this way which equals high vacuum in intake manifold. So they look for other sources of air and try the crankcase via the AOS . Since the crankcase leads directly to the oil filler cap there should be a good vacuum until the spring loaded valve in the AOS closes (If working correctly) due to the difference in crankcase pressure Vs intake manifold pressure because you opened the oil fill cap to atmosphere, at which point the vacuum at the opening to the oil fill pipe should be very little (Valve is closed in AOS which separates intake manifold from crankcase, more or less) until you put a hand/oil cap in the way and seal the opening then the pressures balance again and the spring loaded valve opens and the vacuum re-establishes. There is pretty much only one way to get oil in the intake and down to the MAF, via the AOS ! Most likely a bad AOS , new or otherwise. Less likely is a blow by the rings in one or more cylinders upsetting the above described pressure balance ballet. If the compression/leak down don’t suggest bad rings and you have no pools of oil on the garage floor due to bad crankcase oil pipes/leaking gaskets etc then change the AOS --- again! You said detailed question, did my best to detail my thoughts despite the beer. Hope it helps! Good luck and please let us know the end result. Cheers!

Thanks guys for the continued input, and detailed responses. Just to note, I have never ran the engine dry, as I watch the oil level very closely. For that matter, I have never had any other technical issues, aside from what I mentioned. Also the car is always parked on a level surface. I had the car transported to the dealer on a flatbed truck and the car was raised on hoist at the dealer, so I am not aware of anytime it was parked on an incline. It was just over a week between the car running and the inspection, so it sat for 7-8 days. I had a compression test done previously by Porsche , and they indicated all is well. I am not sure if they checked all cylinders or just 2, as they only provided compression values for 2 cylinders, as per my post. To me this seems like standard troubleshooting process, and I would expect the dealer to know how to and suggest all these tests. Unfortunately it hasn't been this way, so I appreciate you guys assisting me. I think I will try to contact a local indy shop and see if they can take over at this point. I will have the AOS re-tested, and try replacing it again. Please let me know if you guys have any other ideas/suggestions, as I will have the indy look into it while they are re-checking the AOS .

I agree that OP was just following what the manual stated. I don't expect customers who want to enjoy a car to be aware about every last detail. If a car warns it needs an oil change and the owner heeds that warning that is all that should be required. I don't think Porsche expects its customer base to be mechanically inclined in the least. That said to me 20k is quite the long service interval but then again I did 15k for my E92 M3 and I tracked it 3 times a year. But that is because BMW said so and I stuck with that. All I needed to do was add a quart of oil to top off during that interval. I have never had any issues or lack of performance etc etc. However with my Spyder regardless of mileage I plan on doing an oil change every year. It's a fair weather car anyway and I have racked only about 5k miles in a year. I agree with the advice on getting the AOS replaced.

Ok I'm going to throw in my WAG. Since you stated that the oil consumption came on suddenly I suspect a broken oil ring in #2 cylinder. Oil ring break will not show up with compressing or leak down tests. How this bypass oil gets back to the rest of the cylinders I don't know. But I'll guess the AOS has something to do with it. Before jumping in to pull cylinders I would first pull the valve cover on the #2 cylinder side and make sure the valve oil seal cap, use to be rubber in the old days, did not split. Good luck!

The oil ring is an interesting suggestion. That being said, originally the dealer indicated I had oil pooling in cylinder 4, and then on the second time around they said cylinder 2. Overall it feels like I must have oil in all cylinders as its in the intake, MAS, and on all the plugs on both sides of the engine. For some reason the dealer won't let me speak with the techs, instead I need to speak with the advisor. These type of details like which cylinders, how much, etc... only the techs would know as they did the testing. Does anyone else have a dealer that prevents them from speaking with techs? I am not sure if this is something unique in my area or some common Porsche practice. Thanks, VadRad

Where are you located? Sent from my Nexus 9 using Tapatalk

I want say that I had similar symptoms (but not all) as OP and I have to get a "new" remanufactured engine from Porsche (was able to relate it back to prior to CPO ended so ended being no cost to me). I'll be picking up the car tomorrow after being at the dealers for over 2.5 months and more details.

Replace the AOS even if they say it checks out. Vacuum leaks can cause high oil usage.

I know it's been awhile, but did you ever determine what caused your oil consumption? I have an ' 06 Cayman S that has similar oil consumption. Thanks!

Usual dump the problem and run.. when people started suggesting the AOS be replaced he got resistant to the idea, it wasn't jiving with whatever disaster he'd envisioned.. so he left. His last visit here was July 2017. You see this a lot in forums - someone just looking for confirmation that what they've already decided to do is the right thing to do. All sorts of forums - some not even vehicle related. If they don't get agreement with their already made decision they leave and go somewhere else where they hope the crowd is friendlier (or stupider.) As far as your '06 - has the AOS been replaced? That would be the first thing to do. If that doesn't help it's time to scope the cylinders and pray that you don't have any cylinder damage.

Besides bore scoring another thing to consider is valve seals. My '05 had very high oil consumption - 1 qt every 700 miles - which I resolved by replacing the engine. The tear down of the old engine did not reveal any bore scoring but I did have burnt valves on a couple cylinders and bad valve seals.

After reading all the older replies no one talked about the Used Oil Sample Analysis. This within itself is a Great troubleshooting tool!! He did a UOSA early on but didnt say anything about the results he posted. Aluminum 10 ppm the avg is 4 ppm Chromium 3 ppm the avg is 1 ppm Iron 51 ppm the avg is 9 ppm lead 11 ppm the avg is 2 ppm Silicon 21 ppm the avg is 7ppm Based on these results he either needs a new motor or tear down existing motor and rebuild. Used Oil Samples dont lie!! Every Porsche owner should be pulling samples on every oil change which will show the health of the motor or its demise......

Could not agree more. Money well spent. I just got my latest back today: Aluminum: 3, Chromium: 0, Iron: 4, Lead: 0, Silicon: 2. Blackstone Labs.

Can you see if it is running rich? I had the same issue on my Boxster . It turned out to be the injectors.