Macster

the fact the tube carries vapor from the crankcase. No air/oil separator, at least on a mass produced auto engine, is going to remove 100% of the oil in the vapor coming from the engine.

I've only checked for oil at this connection once, when the source of my car's problems (as it turned out) proved to be an AOS going bad. At that time there was considerable oil at the connection to the intake manifold just behind (downstream) of the throttle body. There was oil on the throttle body butterfly valve (which upset mildly the engine's idle smoothness).

If you find any signficant amount of oil there, dry it up and wipe down all surfaces of any oil. Make sure throttle body and butterfly valve clean.

Then button everything up and drive the car normally for say a week and then look at the area again. If oil wetness present, if oil fluid present in any quantity... This could be a sign the AOS is allowing too much oil laden vapor into the intake and in doing so accounts for the engine's excessive oil consumption.

There could be a test/check a knowledgeable tech could perform that could point to a failing AOS, but he's not going to make this test/check without his manager's direction/approval.

I'm not that familiar with the 996 car and engine -- my car is an 02 Boxster -- but when my car's AOS was going bad -- towards the end -- it produced so much vacuum that while engine idling I could unscrew the oil tube filler cap but could not remove it against the pressure difference caused by the excessive vacuum inside the engine. I'm not sure this 'test' is valid for the 996 engine. If it is though, and you perform it, it might tell you something.

As for denying your complaint of excessive oil consumption by 0.1quart I think that's just the dealer stalling you. Have you heard 'they all do that' yet?

But if the oil consumption is getting worse, then even the dealer should be able to notice the excessive oil consumption and that it falls within the guidelines for attention.

BTW, many car makers are going to lower tension rings to reduce engine friction. The downside is oil consumption goes up as these rings are more likely to float/flutter a bit under some conditions and thus not control oil as well. I remember some years ago -- circa 2001 to 2002 -- the new (then) Corvettes were receiving some complaints by owners about excessive oil consumption. Some drivers were driving these cars like 'sports' cars, hitting the upper reaches of the engine's RPM range and letting engine coast down on closed throttle from these elevated RPM ranges.

Under these conditions the rings fluttered quite a bit and oil consumption (under closed throttle there's a lot of vacuum in the combustion chambers) went up quite a bit.

Chevy said essentially -- at first -- stop doing that. But enough owners complained that Chevy sold the car as a sports car and they were going to drive it like one and if oil consumption was a problem under these conditions it was Chevy's problem. In some cases I read where indeed Chevy stepped up and replaced engines -- those with not only excessive oil consumption combined with high levels of noise arising from piston slap -- or re-ringed those with just excessive oil consumption with rings with more tension to better control the oil consumption.

Sincerely,

Macster.

insite

boxster and 996 motors are both M96 & the AOS systems are quite similar. if you've just found a bit of film, it's probably not the problem. if it were, there would be a LOT of oil in there.

a quart of oil per tank of gas is ridiculous. your dealer really has to listen at this point.