Used Air Compressor, odd color oil...

[formula388]

I picked up a used air compressor it is a Porter Cable cplmc7580v2c essentially its a 7.5hp 240v 1ph 80gallon air compressor. Claims 23.5 SCFM at 175PSIG.
I bought it from a reseller who didnt have the ability to show it to me running and told me he never heard it run which made me nervous, but I bought it anyway. I paid $700, knowing it needed a motor pulley and new belts (both of which were way more expensive then I was expecting)
Anyway, when I got it home, I temp wired it and turned it on, filled tank to pressure very quickly, though it didnt hit 175, it his 165 which is more then enough for me.
After hearing it run I let it sit a few days while I ordered the needed parts and new compressor oil and air filter. When I drained the oil it was GREEN...
I have worked on my fair share of machines and compressors but have never seen green oil. Right now I am waiting on the pulley to come in to run it again. I purchased proper compressor oil. Any ideas?

 

[MongoTA]

I've only seen "green oil" once and that was when UV dye was added by someone trying to trace a leak. Does it pop in color under a black light?

I have heard of green oil due to copper in the oil, but I believe that's more if an HVAC thing.

Later this week I have to tear down a small 9hp gas engine that I didn't properly winterize. Thought I was going to do one more late season leaf cleanup last fall and it never happened. I forgot about it and the engine sat outside over the winter. Water got in the oil and when I fired it up this year I quickly recognized that I had screwed up. Drained the oil and while it was dark oil color, it had that sort of milky-swirly-emulsion thing going on that I see in your green oil.

Sorry I cant be more help. Draining that would indeed be a surprise! Hopefully it's simply a surprise and not a disappointment.

 

[Wrench97]

Liquid Moly?

 

[seber]

I've seen green oil on occasion but that looks like it might have water in it. Good idea to change it. Green coloring is added to some oil to indicate from bio friendly sources. LOL. I've also seen it used in very large industrial compressors when I worked for AT&T. I don't have any idea what the reason was.

 

[Wrench97]

I've seen green oil on occasion but that looks like it might have water in it. Good idea to change it. Green coloring is added to some oil to indicate from bio friendly sources. LOL. I've also seen it used in very large industrial compressors when I worked for AT&T. I don't have any idea what the reason was.

I believe some screw compressor oil is green.

 

[Snapped-off]

Reminds me of Penngrade break in oil

 

[The Cobbler]

drain it, rinse & repeat . fill it with known oil or synthetic

 

[WWheeler]

Perhaps this might be helpful...

Understand The Changes In Color Of Air Compressor Oil During Use

Understand The Changes In Color Of Air Compressor Oil During Use

www.mftfilter.com

 

[david3921]

From Wheelers post;

5.Special color change reasons

In addition to the above reasons for discoloration, there is a special case where the color of the oil turns green. After tracking the cases, it was found that when the oil turned green, the acid value was increased and the increase was large. The acid value was detected more than 20 mgKOH/g, even the loose oil change standard. The acid value will be allowed to reach 2mgKOH/g or more, which is already 10 times higher, indicating that the deterioration of the oil is already very serious.

I'm with Cobbler's suggestion;

drain it, rinse & repeat . fill it with known oil or synthetic

 

[Sumboodie]

There are a few outfits that have green oil for hydraulics. It's supposed to be "green" ie... ok for the environment.

 

[Firebrick43]

I think it used to be blue, and turned green because of water emmulsion. The second to last pic has the tell tale sign of water in the oil dripping out of the pipe.

I to would put some cheap 30 weight oil in it. ATF would be ideal as it has a lot of detergents in it. Run it for 30 minutes getting it warm, drain and fill with the correct oil.

 

[formula388]

Thanks for the replies everyone. The last pic is from me spraying brake cleaner into the fill hole to try and get it as clean as possible in there. When I first opened the drain a small amount of water did come out but not too much. I am hoping it is some “green” oil, but either way I will be filling with Milton Air Compressor oil. I’ll change it again after a week or so of use just to “flush” the system better. I don’t know much about the compressor head but I suspect it is a splash style lubrication as there is no oil filter.

 

[MacMcMacmac]

Hydrovane 2000 oil was green back in the day, although a dark green, unlike this stuff. I'd second the Liqui Moly stuff. Seems to match up.