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sand_man sand_man is online now
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Join Date: Oct 2005
Location: Cooterville, Cackalacky
Posts: 6,405
Question An interesting oil consumption observation

...need to file this one under things that make you go "HHHMMM"...

I've come across an interesting oil consumption phenomenon with my engine and was looking for some feedback and/or your own experiences.

My car/engine seems to like the oil level being maintained at the low end of the dipstick. If I try to keep the oil level at the "half way" mark, my consumption goes up considerably until she reaches her place further down the stick. Once there, the consumption pretty much stops. Here is some additional info:

-Very rare smoke at start-up - if there is any, it goes away immediately.
-Absolutely no leaks (knock wood).
-No smoke on accel or decel.
-Using Brad Penn 20W-50.
-After market headers with the small "un-vented" turbo drip tank (factory tank had a vent up to the air box).
-Factory airbox removed, and the hose that connected the crank case ventilation system to the airbox now just has a small air filter on the end.
-My dipstick and oil level gauge match perfectly; both read the same.
-Daily driver, no track and/or DE time.
-Just over 10,000 miles on a total rebuild.
-Engine has NEVER been overfilled with oil.
-I'm well versed in how to check oil in these engines.

I've noticed that when my oil level is at the half way mark (maybe a tad more), there is more smoke/steam/mist coming from the oil filler neck. When the level is down, this steam is mostly non-existent.

I got concerned because in less than three hundred miles I saw my level gauge go from a hint over half way, to a few milimeters above the bottom line. I thought maybe I had cracked some rings during all of the tuning that I've done, to steady state my CIS system, and was experiencing some blow-by. But now not a drop is being used (yes there is oil in the engine ). I will take a hot leakdown and compression test soon...I'm just soooo busy at work and with holidays, I haven't had a chance.

Furthermore, in a few of the oil consumption threads that I read through, a couple users mentioned that their engines also liked a particular oil level...once there, all was good.

I've been told by a few "Porsche engine masters", that the crank case ventilation system in these engines is hideously poor. I wonder if no longer having a turbo sump tank vent is a contributing factor?
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
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Last edited by sand_man; 12-12-2007 at 06:07 AM..
Old 12-12-2007, 06:01 AM
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