white milky liquid

[Afterburner]

My air compressor filter mod (as catch can) usually has blk oil in it. Tonight after 90 miles at around 45F outside.....I looked and it had white milky liquid with slight tinge of brown....is this normal???

I looked at oil dip stick and seemed normal and clean oil. Also took off oil filter cap and no residue.

Thanks for any gudiance!

[ChuckG]

Sounds like condensation, but I'd monitor the situation.

[ToolGuy]

Not a fan of the catch can mod but that said, like ChuckG states, probably just condensation. The engine after 90 miles was warm and burned it off but that can since it is on the outside, so to speak of the engine, most likely did not get warm enough.

Before I stored my lawn mower and changed its oil, I ran it out of fuel while it was cold outside and when I removed the oil cap, I saw the typical white milky substance assiociated with condensation. No problem, normal...

[Afterburner]

Thanks guys. I also had car idling for a while that day since I hadn't started in a week. I changed the filter on compressor mod and cleaned can. I guess I shoudnt idle car and should take it out and let oil heat up at least once a week.

[ChuckG]

Oil must reach a temperature of at least 190 degrees to cook off contamination.

In my case, I can't run full synthetic oil because it never goes that high if the ambient temperature drops below 70F. Early C4s have oil coolers and I only change my oil once a year, averaging about 2200 miles a May-October season.

I got the same kind of residue on my oil filler cap you're seeing when I did run full synthetic. My reaction was very panicked, but an engineer buddy explained the problem.