this is interesting I found this thread towards the top w/o a search; I have 2 compressors at present; both older "EMGLO" brand; a 1977 vintage (they still sell this very unit today under both DeWalt and the "Jenny" name) wheelbarrow type w/a 5HP Briggs engine; only difference? New versions have a Honda engine.... YUKK!
my other EMGLO is a 1987 version, 5HP 80 gallon upright 2 stage 4 cyl pump;
I am noticing something lately, that I remember from my days in the tire/alignment shop, and with other piston compressors I have dealt with;
In my water trap as well as out of the tank when I drain them, I get a white milky, sludgey mess; I recently got the gas powered machine; IDK the history though it was supposed to be "1-owner"; my 80 gallon upright I have had now about 8 years, bought used from a former body shop owner; but never really noticed this til recently (temps were still warm) I admit I don't drain my tank as often as I should, but more often than many I know w/ compressors, who tell me "Yeah I ought to one day, huh"?
Anyway back to the whitish sludgey slimy mess I get out of them; What is this caused by??? I try to stay with a regular 30W straight weight dino oil, same stuff I run in my air cooled mowers etc; but have been known to occasionally top off with what ever I have sitting around and is a less than full bottle;
everything else I have, I run 10-W-40 Valvoline year round; I have no OHC engined vehicles; all Dodge 318s 360s and Jeep 4.0s;
I have never bought the regular "compressor oil", as I always thought that the label was a batch of [censored] to be able to charge more; like buying Briggs and Stratton "small engine oil"... double-plus what even premium oils cost and they only give you like 2/3 of a quart.... I have never been a synthetic fan (synthetic means "artificial"/"fake" right? and it is extremely costly vs a conventional) and the brand, weight, type of oil I have used, has not mattered; I never saw that sludge [censored] from my 80 gallon unit til a few months ago; I am a homeowner and use this for my personal use not business, where it would run non stop;
as a former 18 yr professional alignment tech, I still get calls from former customers asking me to fix their stuff here, as side jobs; I have a glass bead cabinet which I use fairly often; the 80 gallon has never failed to keep up with anything I have thrown its way; incl running a 100 lb pressure pot blaster in resto of a projecr car or most recently a home built trailer I blasted;
I often get water accumulation and I have noticed it very dependent on weather; I have several water traps; so I can keep an eye on that; but regardless how hard and heavy I have used my compressor (or not) or what oil I put into it, the sludge thing just started;
the portable I just got last week, and have run it a few times, "de bugging" it and catching up on maintenance and noticed it right away from that one;via the clear bowl on the water trap (though it is winter in Chicago) I changed oil in it upon the 1st time I used it (put regular 30W in it) growing up my parents had a 2HP Campbell Hausefield, new in about 1976, (I was with Dad when he got it, I was about 9 or 10) still runs fine, and doesn't do this; and oil changes... WHAT oil changes on that unit; I ran the snot out of it in my '80s teen years; and it still don't sludge up.
Neither my parents' or my 80 gallon use much oil at all;(a little but to be expected due to the nature of an air cooled, air compressor) the gas powered one I have not had long enough yet to tell whether it will (or won't) be an oil user; I remember one we had at the tire shop that "drank" oil; but it was very old and TIRED. it would not build the pressure it once did, took too long to build what it did do, and finally got replaced.
I don't mind a little oily residue as I figure it can only help to protect the innards of the tank; but what does bother me is the sudden noticeable increase in the amount of it;
I do not believe my compressor is wore out, it still builds pressure as readily as ever, and like doing a compression test on an engine, it cannot put more PSI in the tank than it can build within the cylinder.... but would this be related to choice of oil in the crank case? what IS "compressor oil"?
I choose to oil my air tools as I use them and not off of a central inline oiler as my glass bead cabinet would not like oil,and I do occasionally use my compressor to paint with... in fact taht was exactly the reason I bought the 5HP gas powered one to take to a buddy's farm where I am doing some painting too far away from both an outlet and the breaker box; I tried a 110V Portable and was spending too much time going over to reset the breaker; compressors don't like 125' of extension cord off a 15A breaker (I tried 2 different units out there) and the owner of the property where I am doing this painting at, asked me about painting that barn come Spring once the weather improves; so having available air that's not tied to an insufficient electrical panel will help tremendously; but I want to eliminate this sludgey [censored] from the line so as not to ruin the paint job... IS the solution as easy as using a different oil in the crankcase???