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Moisture in oil filler tube

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Do any of you regularly get moisture or water +oil milkiness in the oil filler tube? I got home from a three day road trip that out about 500 miles on my 99 C4, and when I checked the oil filler tube, there it was, white crud in the oil filler tube. This isn't the first time I've seen it, either. However, for the past two oil changes I have sent a sample to Blackstone Labs for analysis. Both times I got great reports. I've owned the car since May and have put 19,000 miles on, so it gets driven a lot. The coolant level has not changed in this time. I also own a Boxster, and there's never evidence of moisture in that filler tube.



Edited by jaekormtb
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Correct. It is oil and water condencing on the cold surface of the oil filler tube. It is worse in the winter because the surface of the oil filler tube is colder. I drive my car in the winter also and it got pretty messy. Interestingly, It has not happened since I switched to Millers Oil CFS 5W 50. I can only theorize why this might be the case. The oil and water vapors condence together on the cold surface forming an emulsion (the white stuff.) This traps the water. The emulsion has a much lower vapor pressure than water alone thus in order to get rid of it you have to heat it to a higher temp. Higher than the surface of the oil filler tube ever gets. So, the stuff just collects. My guess is that the Millers has a lower vapor pressure than Mobil 1 0W 40 thus only water vapor gets up into the filler tube, an emulsion does not form and the plain water condensate can evaporate with just a little heat. No white stuff.

I am headed into another winter with the Millers so, we shall see what happens.

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That is an interesting theory. Does it have a lower vapor pressure point because of it being 5W50 or 5W40 in BAD124's case, ... or due to some other unknown factors in your best estimation?

I run Mobil 1 0W40 in Pacific NWest winters and do get that green-yellow type of mayo as well. I do wipe it out from time to time to make myself feel better.

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Mijostyn - interesting theory. Since I have been adding much less oil between changes with the 5W40, my though was that it was volitizing less and therefore creating less "vapor" in the crankcase and in turn, oil filler tube.

I can see how cold weather would exacerbate the condition, but I was getting the filler tube buildup even in warmer weather (70-80 deg F)

Just for comparision I went from M1 0W40 to Liqui-Moly 5W40, both full syn.

Consideing 5W50 for next summer

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