Oil consumption

Greetings everyone. I have been an avid reader of Rennlist for a couple of years. This is my first post in this forum. My 2002 996 C4 conv. had it's rear main seal replaced 2x, the first I paid and the second the dealer covered the cost, mileage is 41,000. Prior to the main seal replacement the 996 required 1 qt of oil every 600 miles. Post rear main seal, it consumes 1.25 qts every 300 miles, no smoke or oil drops noted. To say the least, this has me very concerned. The dealer has always maintained that the 600 mile consumption is within spec. I have not spoken to the dealer regarding this concern and I am hoping to get some feedback before I approach this subject. Originally I had purchased this car with 24k miles. My 2007 997S with 4K miles has not consumed a single drop, even though I track it on a monthly basis. What's up with this? I really love the 996 and won't even consider selling it. Current Vehicles: 2002 C4 Conv 2007S Conv 2006 Cayenne Turbo 2001 Honda Accord, my daily driver/bread winner 2004 Cayenne S sold and forgotten

Doesn't sound right You sure your bell housing isn't filling up with oil?

Have you tried a better oil?

Greetings! I just wanted you to know that you are not alone . . . While I have not had a RMS problem, my oil consumption has "went south." I am really surprised they will not take action as you are well below the magic number of 1 qt per 600 miles. Funny, also like you I really like my 996, and will do about anything to keep it going. [OT: Why do Porsches do this to us? My Toyota has never been in the shop, burns no oil, has no creaks anywhere, but also has no emotional attachment . . .] FYI, here is my story on this: Situation: Oil consumption on used 2003 996 C4S was running about 1 qt per 1500 miles. Not great, but not bad (no need to chime in if you have zero consumption just to make me feel bad ) Then over the winter, as I drove the car, it went down to 1 qt per 600. So I figure I will head into the shop for a check. They do a formal oil consumption check, which, by the book, involves topping off the oil cold, driving 600 miles, then reading it cold. Now the annoying part (minor rant). They confirmed 1 qt per 600 miles, but then produced a TSB that stated 1.1 qt per 622 miles was the actual standard, thus they could not look into it. Since I am an engineer by trade, I pointed out that a dipstick is hardly a precision instrument. However, they sent the query on to the regional technical manager (probably an accountant) who denied action. FYI: Never any smoke. Might be excessive soot from right exhaust, but some from left too. The car runs really quiet, no obvious power loss that I can tell, no weird sounds, no drips anywhere. OK, I have a year left on my CPO, so I can wait a few months then go back in for a precision dipstick measurement, but I was also thinking of taking some action (at my expense) now. One item that comes to mind from other threads on this is to try the 2 chamber Porsche Motor Sport oil separator. Porsche OEM-996 107 926 00. At least even if this did not help it would be considered an upgrade from the stock unit.

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Welcome Your oil consumption sounds a little high in my opinion. How often do you drive it (daily driver or once a week)? Mostly long trips, short trips or both? Has this consumption rate been consistent or does it fluctuate quite a bit?

Guys, this sounds absolutely abnormal. I drive a 2000 C2, have the same engine, and can't even remember the last time that I had to add oil to the car. I might guess it's every 5000 miles. Maybe it's because of my routine annual oil change? Anyway, I would definitely get myself into a different service tech and have the car looked over.

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Hi! I am not sure if the OP still has warranty via CPO, but a dealer will not look at anything (at least my dealer--limited choices here) unless your consumption hits a certain level.

it may not appear its burning oil... but it has to be going somewhere. Do you have a sweaty oil bellows (bellow the air oil seperator) it is located under the driver rear axel area?

True, you may only have a leak under high oil pressure, so you would never see any onthe garage floor. No dealer in their right mind would say a qt of oil per tank of gas is normal...& I still think a qt every 2 tanks is still very high.

I never need to add oil to my 2000 C4 between changes. Boxster was another story which required half a quart every 1,000 miles or so.

Gregory, I never had it with my Boxster S either. A friend of mine has been commenting about using a lot of oil in his 997S. He tells me that it's about 1 quarter every 1000-1500 miles. The service tech says that acceptably, but I am stunned that I never really seem to be adding oil between changes. Odd. Have you checked on RennTech also? They may have some experience with this also. UPDATE: This post had some pretty good insights that may pertain to you.

Porsche dealers seem to quote the 1qt every 600 mile cut-off as there threshold for reviewing if there is an issue. Clearly that has been passed in this case. 1.25 qts every 300 miles is like running a 2 stroke engine! As other have pointed out, it's either going somewhere or being burned during driving. Note - the 996 can exhibit a high moisture content in engine oil when used for repeated short trips. This moisture can then 'burn off' on longer trips, giving a visual impression that the oil level has decreased - worth bearing in mind, depending on vehicle use patterns. Are you noting that the oil consumption was a step change when the RMS was done - or are you just using that event as a time marker?

I have over 115k miles on mine, and it burns ZERO oil between changes (around 7.5k). The electronic gauge doesn't move, and the level on the dipstick confirms.

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You better bring it back to the dealer so they can correct your obviously, faulty engine.

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Yeah - I think it's gonna blow-up anyday now.

lol torrente, For comaprison my 99 996 and 03 Boxster use no noticable oil between yearly changes.

My C4S with oil changed in April, this weekend burnt through 1 litre of oil/per day, driving conditions for each day: 80 min aprox 140 km at 5000 to 7000 rpm. 80 min aprox 80 km driving 2000-5000 rpm and 150 min 300 km driving at 2000-3000 rpm. In total for the day 5 hours of driving a distance of aprox 520 km 1 litre of oil and 2 tanks of gas.

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You realize you're driving a two stroke Porsche at this point, right?

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modified my original post a bit, but yes the consumption is very high when under heavy load. This is me at the track driving the car full out and always at peak hp. Then my wife at the track taking it easy and then the drive to and from the track and a trip to the gas station under very little load. I just checked my oil level this morning after 2 days of this and it is now at the last bar before it reaches min. So that is 3 liters it's gone through. Anybody else burn this much oil tracking your car? My RMS is sweating but there hasn't been a drop of oil on the garage floor. I did have slight smoke up at startup once this weekend and no one behind me at the track noticed any smoke from my car while on the track.

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Well it's all going somewhere, either that or your bell housing is filling up! Suspect that it's all burning-off in use - but it's still quite a throughput. You getting a lot of soot in your exhaust pipes? Only other point of inspection I'd suggest could be the air/oil separator bellows, they can puncture and leak (not good).

I am not getting abnormal sot on the exhaust pipes. This winter a did 4000 km and put maybe 2 liters of oil in the whole time. I drive it short distance daily and fill up the gas tank once a week. Maybe once a month I need to put in 1/2 liter of oil.

pull the oil separator tube off your throttle body and see if there's oil in it. if there is, the membrane in the oil separator has gone bad and you're sucking oil in through the throttle. this is probably the most common cause of your problem on the M96 motor variants.

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Thanks for the very useful suggestion. Just so I do not do something stupid, do you (or anyone else) have a photo or schematic? Thanks again!

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here's the best i can do. the end of the tube circled in red on the left connects to your throttle body. the pic on the right is the engine. this is a boxster engine, so the red tube / throttle body are rotated 180 degrees on your car (they'll be to the lower left in the pic instead of the upper right). the throttle & oil separtator tube will face the back of your car. the tube is on the side of the throttle and is about 3/4" in diameter. to undo the tube, pinch the plastic collar and pull it off the throttle. dip your finger in it. if there's oil in it, you have found your problem. FYI, a new oil separator is about $100 from sunset imports. it's a pain in the butt to install. unless you're patient & wrench savvy, pay the guy.

Thanks!!

Here's a photo of the actual separator - outlined in red (again 986 Engine) When mine died (986) It made a noise like a blue whale falling from 30,000 feet - so I was lucky to get an audible clue as to the issue and it's location!

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right out of engine. Even if engine subjected to a bit more vacuum at the inappropriate times, vapor more heavily loaded with oil droplets will be pulled out of engine before the separator has time to remove these and this oil will be burned. 'course, you have to have engine checked over very thoroughly for any oil leaks. (I had another car that leaked oil, but nothing showed up under car, or anywhere on any other car parts. The oil was dripping out a valve cover gasket down on to a hot exhaust manifold and the oil was being vaporized from the high heat of the manifold. The leak would subside before exhaust cooled enough. The only way I knew oil was leaking was I smelled it when I shut engine off and sometimes when I started hot engine I'd see a puff of what was oil vapor coming out around hood gaps. Service manager looked engine over and to his credit spotted stained area on exhaust manifold that was from the oil dripping down on it when hot.) An engine has to really use a lot of oil for it to show up as smoke in the exhaust. When it does, usually it comes during a time when the engine is not actually burning any gas -- like on closed throttle coast down -- so the oil goes through the engine unburned and what you see is oil vapor. One 'trick' is to with sun low behind you drive car and watch for a haze/light light smoke. With sun high overhead or facing you as you drive car... Be very sure you accurately document oil consumption before you go to dealer. Do not rely upon memory, but sketch the oil level on dipstick and check oil after car has sat unused for some length of time. Or take pictures to show the oil level and mileage and how the car has been parked. You want to be very scientific and thorough about this, not haphazard at all. I'd start with fresh oil/filter with oil of proper brand, grade, etc. Add an exact amount, say 9 quarts (just a number, use the right amount so oil level not too low or too high) and after letting engine sit idle as long as you can -- overnight -- check oil level. Note very accurately its position. Do not rely upon your memory. Note odometer reading. Then every fill up, or every day even, at some parking space, check oil level and note its new level and odometer reading. You want enough readings that show oil consumption excessive and clearly so. If you don't do this now, dealer will likely require you to do it before it does anything at all. Also, mention that with this high oil consumption you have lost all enjoyment from use of car, are concerned the high oil consumption is precursor to serious engine trouble, possibly subjecting you to safety risk if engine fails on busy highway in rush hour or leaves you stranded late at night. And so on. If it applies in your area, you can have car checked to see if it still passes smog and if not, then use this a some leverage to have engine fixed. Sincerely, Macster.

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Excellent post! agreed with everything stated here! Especially with the documentation part.

This has been really helpful. I removed the tube and there was an oil film inside. Given how the separator works, I am not sure if this is more than average--is it ever completely dry in this tube? Still worth looking into. Thanks much. I would just add a note to Macster based on my experience of a couple of months ago. Even though I had completely documented a change in consumption over the winter (a COLD winter, FYI) my dealer would do nothing without their own oil check. It came back just short (actually 0.1 qt short) of where they would take action. As an engineer, relying on a dipstick for 0.1 qt accuracy is pretty silly. Will just redo the test later this summer.

A light oil film inside the tube is normal and is not an indication of a problem.

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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.

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.