# Sludge on the oil cap -- what is it?



## boriska00 (Sep 24, 2006)

Good day everyone.

I opened up an oil cap the other day and noticed some brownish sludge on the cap and around it.  Attached photos will show you what I'm talking about.

I've heard that whitish sludge will indicate antifreeze leaking into the engine and mixing with the oil, but this thing isn't really white. Is it just dirt?

Here are a few facts about the car:

It's a 2001 330i, 135k miles. The car isn't driven many miles per day, so it take a long time to get to required 14k oil change interval. It's been about 11k since the last oil change and probably over a year. It was just a little low on antifreeze (i'd say 10oz, maybe not even that), and antifreeze hasn't been changed/flushed for several years now.

So the question is what is the stuff I'm seeing? Just dirt because of not changing oil for a while or something else?

Thanks for all your help!


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## DHC8 (Feb 22, 2007)

The oil cap is a relatively cool part of the engine. What you see is most likely water from condensation mixed with oil. It is not sludge in the normal, and feared, sense. A few good long drives would probably make most of it disappear.

That said, your usage pattern of low miles and apparently short trips is a strong argument for more frequent oil changes. Water in the oil, even from condensation, is not a desirable thing.

Internet opinion, take it for what it is worth.


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## boriska00 (Sep 24, 2006)

Thanks!


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## boriska00 (Sep 24, 2006)

just curious, what would the "real" sludge look like?


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## DHC8 (Feb 22, 2007)

boriska00 said:


> just curious, what would the "real" sludge look like?


Google "BMW Sludge" (without the quotations) using their Images option. This will give you a good selection of pictures.

Sludge is like a blocked artery--you get little or no notice until one day a blockage stops the flow of oil. And then the situation deteriorates rapidly.


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## Ethirtysicks (Nov 10, 2007)

Actually, at the shop when i see that it usually means a cracked head or head gasket. thats what it looks like when coolant and oil mix together. id'd roll down to the local autozone and pick up an engine block test kit.
good luck....


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## Lbert (Oct 6, 2006)

I agree with DHC8, due to short trips and cold weather of Chicago, you have a lot of condensation. Change oil more often. 

Sludge is black and gooey.


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## Ron_L (Feb 12, 2007)

DHC8 said:


> A few good long drives would probably make most of it disappear.
> 
> That said, your usage pattern of low miles and apparently short trips is a strong argument for more frequent oil changes. Water in the oil, even from condensation, is not a desirable thing.
> 
> Internet opinion, take it for what it is worth.


X2. Get an oil change, take a couple of rides (30 minutes or more) now & then. It should go away.

However - do you see any oil in your coolant...?


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## jesimmons (Jan 11, 2008)

boriska00 said:


> just curious, what would the "real" sludge look like?


Here's a good example: :yikes: http://bimmerboard.com/forums/posts/314657


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