Loosing oil somewhere?

I had a big service carried out on my 2006 Cayman S about 2 months ago and had covered about 300 miles in it till yesterday. I'd already had to top up the oil once but I thought this was down to it needing to settle and perhaps to mechanic didn't want to overfill it, he gave me 3/4 of can anyway so no problem. Yesterday went for a nice trip to the coast but had to put quite a lot of oil in as the dash was displaying the level as 1 digit at the bottom, the display stayed on too! I can't work out where its going? I've also had an engine warning light come on a few times since ownership which was P2187 & P2189 - System too lean at idle Bank 1 and 2 The car has an aftermarket CAT back exhaust. The service mechanic said this could be the cause of the error codes. He did say the PIWIS system didn't say or show anything obvious that explains the error codes or that the O2 sensors were throwing errors. I have checked the vacuum effect on the oil filler cap whilst the engine is running to see if the 'Oil air separater' is faulty and noticed a little bit of sucking.... I'm not sure I know what I'm doing really or if my check is valid but I wonder if this could eat all this oil? Obviously I've checked to see if there is oil dripping from underneath the car and its clear and I've not noticed smoking. Any words of wisdom appreciated. Sorry I just realised I should have posted this in 987 Cayman and Boxster Problems and Complaints Not sure how to redirect it....

I don't know where the oil is going either, but something in my brain says don't be so sure that you are losing oil. You aren't dripping it. And you aren't burning any. At least you don't have any evidence of that. And both would be pretty obvious. So that suggests that you should suspect the oil level monitoring system, at least. For me it isn't that difficult to double check because I have a lift. So I would drain my oil into a clean measurable container and verify exactly how much oil is in my motor. Or put another way, oil is the lifeblood of the motor. I need to KNOW the TRUTH about the volume of oil in the motor. Especially if something isn't adding up. Sent from my SM-G988U using Tapatalk

Sounds like the AOS is starting to go. Mine does the same thing and eats about 1 qt. every couple of tanks. Now, these engines do eat some oil but the it's usually something like a qt every couple thousand miles.

Thanks for your response. I do hope its not a dodgy monitoring system, I chucked in at least a litre yesterday :-( One thing I will say is the level has been only going down and after our drive to the coast yesterday it is down a digit or 2 from the top already. The exhaust tips do get sooty, perhaps I'm burning some and spitting some out and maybe the AOS is to blame? Hmm I think I need to get under the car and drain it to be sure as I too 'NEED to know the truth' !! All a bit scary.

Thanks, I'm gonna check the oil physically with a drain to confirm to myself the monitoring system is functioning properly and I think just replace the AOS too.

firstly the sensors are quite sensitive...it can go slightly up or down depending on how its driven. check your plugs to see if you're burning any oil. if the AOS has never been changed it might be a good preventative measure anyway - just make sure to get a good one!

I think this sounds like it might be a failing AOS as well. I just had mine fail and it started eating a lot of oil. I got cat errors and misfire errors. I believe that when you get too much oil going down the throat of your engine it fouls the plugs and cats and can give weird errors. I switched out my AOS for a genuine Porsche model and I have driven 800 miles without a code. Whereas I was getting rough idle and codes almost every day before. I am also not using any oil anymore. Pulling off the oil cap while the car is running and feeling a slight suction is a good test. I think a better test is to remove your engine cover and pop off the AOS line to the intake and see if you have any oil in there and how much.

I've read of pulling the oil filler cap and testing for suction, but haven't seen what you are looking for? No suction? Light? Strong? I recently replaced my AOS simply because I didn't know if/when it was last replaced. Now I know!

I've found when the AOS is bad there is light suction when you remove the oil cap when the car is running. It's more of a sound rather than a strong physical pull. After I replaced mine there was zero suction sound and zero pull at all. Also keep in mind when you do this test you will always notice a change in RPM. So keep the engine idle changing slightly separated from the sucking sound in your mind. I only really noticed the difference after comparing the bad AOS with the new. It is subtle. This video is terrible and you can't get the actual sound from my crappy phone mic, but here it is anyway. AOS TEST

I did feel a slight suction at the fill neck prior to replacing my AOS. Haven't checked since (but its easy enough to do that I should try it and see if there is a difference).

How many miles are on the car? Is it running rich (large carbon buildup on the tailpipes)?

It has 102,000 miles which is not too much considering 15 years age. Service history has been fairly consistent, a couple gaps of 2 years or so between services but on the whole I think well maintained. There is carbon build up on the tail pipes though so either running rich or burning oil.....

I've order one from my Porsche main dealer. Actually slightly cheaper than from Design911.co.uk and the 20 mile trip to the dealership is worth it for the walk through the showroom 😛

JPCayman- You might have found your AOS answer by now, 7 months old thread, but its still a great topic as two different items may be involved. 2006 S, M97 engine has port injectors may need some cleaner fluid in the gas tank and a switch to the lowest NOACK oil evaporation product (Redline High Performance engine oil). #1. Redline High Performance, #2 AMS Oil Signature, #3 Pennoil Ultra (cheapest). If your oil burn problem is not due to the AOS failure, have you cut apart your oil filter to see if you have any cylinder side wall/piston skirt particles present? A bore scope can eliminate a bore scoring possibility. Once you have eliminated the AOS and bore scoring as a cause for oil consumption, I would change to a low NOACK oil of your choice.