Oil consumption after LNE retrofit

Could be purely coincidence - yet I don't really believe in such a thing - my 2004 C2 previously used about 1/2 quart of oil between oil changes at about 5500 mile intervals. I had the dealer install the LNE retrofit IMSB 4,000 miles ago and I have since consumed over 2 quarts of oil. I will mention it to the dealer but I expect their reply to be that it is normal with 80k miles on the engine. Seems very odd to me that the oil consumption would increase so dramatically in such a short period of time. I do not see any evidence of oil leaks and the car doesn't smoke at all - so I wonder where the oil is going? Anyone have a similar experience or any thoughts? And I did have the AOS replaced at the same time.

Was Rms replaced ? Oil could be blowing out but you still don't see drip on floor. I have rms weap .. Using 1ltr / 2k miles .. Will fix when clutch due ....

Sounds like you got a questionable "new" AOS unit to me with a weak diaphragm. The IMSB will not alter oil consumption. We have received new AOS units that were bad out of the box, right from the dealer. Its imperative that each unit is tested before installation due to this.

Thanks Jake.

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Exactly right. I have for sometime now suspected marginal/sub-par AOS's accounting for high levels of oil consumption. My belief is these AOS's suck even when they are not failing.

Jake/Macster - I just did what I think is the shade tree mechanic test. Car at full operating temp, A/C off, engine running, removed oil filler cap with no resistance. Slight hiss, but can't feel a vacuum draw with my hand over the filler tube. Idle remains smooth but gradually increases by about 300 rpm. Does this indicate an okay AOS or is the manometer test the only sure way to go. Downside is I bought the part from Sunset Porsche so I doubt the dealer would cover labor under warranty - even though (to quote Krazy) the bonehead tech said that they "never had a bad AOS out of the box and they replace plenty" so he suggested I save a few bucks on the part.

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One AOS failure sign is excessive low pressure in the crankcase. Based on what you posted AOS failure is not happening. But it was not outright failure I was talking about. It is my belief, my suspicion that even when the AOS is not outright failing its performance is marginal. But, and this reads too convenient, it is intermittent. By way of some example I offer my Boxster: Sometimes the engine smokes upon start up and sometimes -- most of the time -- it does not smoke. Yet my driving style, my post cold engine driving and my hot engine shut down routine is well, routine. My point is that given other things are I believe the same or close enough to not have any measurable effect the engine smokes sometimes. What I attribute this to is the intermittent nature of the AOS. BTW, I'm not the only one who experiences this smoking/not smoking, to state the obvious. Many owners report inexplicable smoking events that are not preceded by a short trip or extreme thrashing of the car before engine shut down. But is the above sufficient to justify replacing the AOS? No, of course not. And this has been the case when I've covered this with owners with engines that otherwise inexplicably use excessive amounts of oil. My point is what is needed I guess is a way to measure/monitor AOS performance during a trip or series of trips and note if it is showing signs of intermittent but subpar performance. Oh, in the meantime all I can recommend is you keep an eye on the oil level and be sure you are accurately and reliably measuring the oil level. IMHO, more engines are condemned for excessive oil consumption by shoddy oil level monitoring than actual excessive oil consumption.

Is there any value in going with the motorsports aos I've seen on suncoast parts instead of the standard model ( for a car not tracked)? Longer life, better, etc? I think the motorsports model is several times the price of a regular aos.

Thanks Macster. I pay attention to the onboard measure and then use the dipstick (love that we at least still have a dipstick). I check the level when cold, usually after the car has been parked in the level garage overnight. I will simply keep an eye on it. I relate to the "routine" - mine has been the same with this car for almost 6 years, that why I was somewhat surprised about how much oil I have needed to add over the past 4k miles. Thanks much for your input and advice - much appreciated.

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Well, it reads like you are approaching this oil consumption monitoring in a disciplined manner. The IMSB is so far removed, literally, from the combustion chambers I can't imagine how an IMSB upgrade could affect oil consumption other than possibly by the inadvertent creation of what should be a very obvious oil leak. Have switched brands/viscosity of oil lately? Have you changed your driving, how you drive the car, the type of usage? More idling, high rpm blasts, or just operating the engine in a higher rpm range, all work work to increase oil consumption. No need to respond if you don't want to. I ask the above to get you thinking about what other factors could be affecting oil consumption.

is AOS something that needs to be upgraded on 3.6 engines only.... all of the AOS posts I have seen and there have been many... nobody with an early 996 3.4 engine seems to have a problem with this part... ??

I haven't yet with my C2 MY99, but I only have 64k miles and 12 years so far.

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After giving it some thought I can't think of anything that's changed, same oil, same driving style, car runs as strong and smooth as ever, starts quickly (no indication of fouled plugs) no smoking that I am aware of. The only thing that changed was the mechanic being in there but I agree with you that if he botched the installation of the IMS seal I would think that with over 2 quarts of oil I would see an external leak by now. They didn't replace the RMS, but I personally saw that it was dry and the tech suggested to leave it alone. I'll continue to monitor, and enjoy the car, and will mention it to the dealer. They aren't going to be happy with me because I am still discussing how it is that when I took the other car in for the engine swap that my cats were fine, I was there when they diagnosed the engine noise and personally saw the tech put his stethoscope on the mufflers and cats. They swap an engine and now want $3,100 to replace the right side cat and claim that since it is not dented they didn't accidently drop it or cause the cells to come loose. If the Cat was clogged or throwing a code I might be willing to chalk it up to coincidence. But to me, it defies logic that at 38k miles the cells are breaking down, but I could be wrong. Thanks again

Sounds like its time to go elsewhere to me.

Actually I see more MKI AOS replacement threads than MKII, because when I was searching for them to do my '02 (totally pre-ventative) all I could find we're MKI replacements. And the MKII is totally different in mounting, no bellows, goes in straight down not sideways, and is a bigger PITA to replace.

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Can someone enlighten me on how this may be done?