Re: 328i E36 Yellow gunk inside oil cap

["Mike Klein" <klein@xxxxxxxxxxxxx>]

I investigated this recently myself; here's what I learned.  The yellow
stuff is water condensate.  Because the oil filler area tends to be the
coolest part of the oil system, any water vapor in the oil system will
generally collect there.  Small amounts of water in the oil is normal as it
condenses from the air (or, I suppose, possibly from the exhaust
condensate?); if you don't drive enough to boil it out of the oil system, it
will slowly accumulate.

Interestingly, there is a difference in this regard between dino and
synthetic oil, according to my (Porsche) mechanic.  Synthetic oil mixes
somewhat with water, resulting in less separation of oil and water, and less
condensate.  This doesn't mean there's less water in the oil system, just
less that is separated out and condenses at the filler.  My mechanic doesn't
like that, especially if you don't drive it enough to boil the water out
regularly.  Dino oil and water don't mix well at all and there will be more
water condensate at the filler.  For relatively short driving habits, he
actually recommends dino oil.

                -Mike

'98 323iC, Avus Blue, 3k
'87 911 Carrera coupe, Venetian Blue, 86k

- --On Tue, Feb 23, 1999 7:07 AM -0500 bmw-digest
<owner-bmw-digest@domain.elided> wrote: 

> Date: Mon, 22 Feb 1999 21:56:30 -0500
> From: Len Lescosky <Lescosky@domain.elided>
> Subject: 328i E36 Yellow gunk inside oil cap
> 
> I checked the oil on my 1997 328i and saw I needed to add some oil. When
> I removed the filler cap I saw yellow sticky gunk and some water
> condensate inside the cap. Fearing the worst, I checked the coolent
> overflow reservoir. That looks fine, no oil in there. I stopped by the
> dealer to ask about this. The service manager checked it out with the
> technicians. They think it is exhaust condensate that is not leaving the
> engine because I do not drive far enough. My commute to work is about 5
> miles of 30-40 mph. The temperature gauge hits midpoint at about 3
> miles. I do longer, faster driving on the weekend.
> Have any of you seen this before? Should I investigate this further?
> The car has 14K miles, I bought it from a dealer in December 98, and I
> believe it was previously owned by BMWNA.

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