I have a 51k mile 2003 996 with the X51 kit on it. I am experiencing very significant oil loss. I say loss because I see nothing actually burning out of the exhaust pipes, as I have with others cars I have owned in my life. I have absolutely no oil leaks and a spotless engine and garage floor. I am losing about 3 quarts per 5k miles (basing this on how much I have to add on occasion). My oil comes out clean during the oil change, as it should since it is mostly new. I catch a whiff of oil after I get out of the car but still not a single sign of it anywhere EXCEPT for on the left (drivers side) tailpipe. The tailpipe is discolored a bit with soot but I can't seem to see any smoke or oil anywhere. The soot wipes off fairly easily. Oil pressure generally runs close to 5 for a 4th gear 60mph run. There are no codes, lights, anything other than my oil level showing me the loss. Anyone have any clues?

 

Well, it's going somewhere for sure. Do you have long drives or short drives ( city / open road) and how long does it take you to do those 5,000 miles????

 

look in the coolant reservoir... (just say a quick prayer before you open it up) and if it looks like a milkshake your a victom of intermix.

 

I just finished a 1200 mile round trip and had to replace a quart. I have not found a pattern for whether it disappears faster city or highway. Most of my driving is city but most of my miles are highway.

 

I have a 2002 C2. I had it since new and used to burn 1 qt every 1600 miles, regardless of how hard I drove it and how old it got.

I had the engine replaced at about 140k miles. With the second engine, it doesn' burn anything. I can go 5k miles and not use even half a qt.

I think some engines just burn a lot and some don't.

b-man

 

I think you may be correct, I have a 2003 C4S and I never have to replace oil, I do change it every 5k or 4 months which ever comes first.

 

Oil is always cheaper then an engine. I would suspect your burning it, and it's just not enough to cause noticeable smoke. Sounds like a piston ring or cylinder issue.

 

That would certainly be significant to me as well.

 

Yes, your car's engine uses a bit more oil than some and less oil than other engines. Porsche IIRC gives an oil consumption of something like -- in USA units -- 1 quart per 600 miles so your engine isn't using nearly that much.

As long as the engine runs ok and doesn't smoke -- drove behind a new Jag today for a few blocks and I noticed a bit of oil smoke out of both exhaust outlets -- relax. Just keep an eye on the oil level and don't let it get too low.

 

I had a similar, but slightly lower, oil consumption rate and it ended up being my AOS. Do a search, it's a fairly common problem and I'm assuming you haven't already done this. I had it done along with my nasty yellow coolant expansion tank and it's much lower now.
GOOD LUCK!