Greasy gunk from Air Compressor

I drained the moisture out of the tank of my air compressor a couple days ago, and when I did it, this yellowish greasy substance was "mixed" with the moisture/water that came out of the tank.
At first, I thought it was the compressor oil, but I check that and the level was fine....plus, compressor oil isn't yellow. And this yellowish substance isn't rusty colored...it's yellow.... I'm baffled. It's a 5PH 25 gallon Campbell Hausfield compressor. And, I've drained the moisture before and never experienced this.
Anyone have any idea what this could be?
Mark
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Oil, water, and a mix of some of the dust in the air that gets sucked in. Makes for a nifty emulsion.
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Ed,
Have you seen this type of yellow gunk or are you just suggesting a possible cause. The compressor is located in the basement, and it's clean as far as basements go. It's gotta be the compressor oil, but I'm not losing anything...and this is the first time in 5 years of owning the compressor and multiple times draining it.
Mark

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Mark wrote:

its oil-less. Orange yellowish, greasy, foamy gunk that leaves a rusty stain when the moisture evaporates, that it?
--
Grandpa

What is that dripping from my fingers?
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Exactly what I had...orange yellowish greasy, somewhat foamy gunk. Every time I've drained this compressor before ( or the compressor I had for 15 years prior to this one) I've never seen this stuff...it used to be just rusty water that's not greasy.
And if you are getting this from an oil-less compressor, where in the heck is the greasiness coming from? The air? Didn't think the air in my house was greasy!!!
Thanx Grandpa!!!
Mark

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Tiny amounts of oil and other gunk from the air will combine to make an emulsion. If you have filters in your heater or air conditioner, you know they pick up all sorts of stuff from your clean air.
We use a lot of air at work. The 850 cfm compressor runs 16 to 24 hours a day. The automatic drain has a system to separate the air and oil and it accumulates by the gallon. Water goes to drain, oil or other contaminants are drained into a 5 gallon pail that fills every week or two.
As for the compressor being 5 year sold, it is more likely to have blow by now than 4 years ago. It does not take much to make a creamy mess.
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What you have is oil and water mixed.

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