Air Compressor Oil

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I just purchased a McGraw air compressor from Harbor Freight a couple days ago. I poured in the oil that was provided, which was nearly .... crystal clear. After only about 10 fill cycles, the oil is already a mid-gray color looking at it through the sight glass. I want to get those break-in metals out and I want to avoid the sump starting to sludge at all.

I assume I should probably run the compressor until the sump and oil are pretty hot and then pull the drain plug.

I wonder if I should fill the sump with some 20wt motor oil... heat it up again and dump it immediately.... just as another flush.

Then I am wondering what to pour in for longer term????

The compressor is in my garage and is only used occasionally.... maybe 2-3 times a month in the winters. In the summer it is used much more. It also gets cold here in the winter, easily down to the negative 10's in January and February, with the garage dropping close to freeing.

I don't mind paying a premium for great synthetic and I can easily get Royal Purple Synfilm 100. (I will not use motor oil, as I don't want the risk of additive build-up.) There seem to be other, great oil choices, but they are sold in only gallon or 5 gallon jugs/pales.

This 20wt is also available from Amsoil. Link CLICK

Any other opinions and/or suggestions?


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Depends on what your manual says, but I am assuming they'd prefer a 30 Weight non detergent oil rather than a 20.

Get the oil stirred up and do a drain and fill with your choice of oil. If you're worried, maybe fill it with a cheap 30 weight ND and use that as the final rinse before adding the good stuff.

Ingersoll Rand has an "all season" oil that's around $9 a quart at Tractor Supply IIRC. Judging by the name, I am assuming it's synthetic.
 
Originally Posted by BigJohn
It also gets cold here in the winter, easily down to the negative 10's in January and February, with the garage dropping close to freeing.......

Operating it in freezing conditions can cause problems. When I purchased mine, I was living back in Illinois. In the Winter the provided oil got too thick, and would trip the breaker. I drained it and put in Mobil 1, 0W-30, and after that it would start up and run effortlessly on the coldest of days.
 
I always add a little oil with a "tackifier" in it... like chainsaw bar chain oil.

If you don't use the compressor for a long time, the tackifier will keep internal stuff oily - and fight moisture (always a problem)
 
Synfilm 100 is excellent run it in my 7.5 hp at temps above 15F below that little iffy.
 
My Quincy specs Quincy oil and filters for its extended warranty. The compressors at work use synthetic oils of differing pedigrees depending on type of compressor. Some of the big multi-stage types use an ester based synthetic.
 
Aren't you suppose to start them with the valve cock open when it's cold until the motor warms up a bit?
 
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I run AMSOIL's compressor oil in my Kobalt 80 gallon compressor. Oil has been in it for 6yrs and still looks good through the site glass. To me for the cost, why cheap out. Throw a quality synthetic in and it can only pay it forward down the road as to putting in mineral oil. Not like you change it out very often.
 
Originally Posted by Chris142
Amsoil makes a compressor oil.

Yup, I've been running their ISO100 in my compressor for years after the initial fill. Seems fine and although pricey, you don't need much in a typical compressor. It's available pretty much anywhere Amsoil is sold. I picked mine up from Weaver off the shelf.
 
Ran to Big R and they had this for sale for $3.99 each. I purchased two.....

Heated the compressor up.... dumped the factory oil. Filled with Mag1...... heated up again and dumped..... and filled with Mag 1. Each fill took about 7 oz... so I only used one of the little 16oz bottles.

Oil was filthy dirty on the first dump and only slightly dirty on the second dump.


[Linked Image from i.imgur.com]
 
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Originally Posted by Duffyjr
Aren't you suppose to start them with the valve cock open when it's cold until the motor warms up a bit?



Compressors have Unloaders, Cheaper ones unload via a schrader in the pressure switch, Commercial/Industrial units have a Centrifugal Unloader.
The short burst of air escaping when the unit shuts down at the pressure cutoff IS the Unloader doing it's job.

Continuous run compressors are different.
 
Originally Posted by clinebarger
Originally Posted by Duffyjr
Aren't you suppose to start them with the valve cock open when it's cold until the motor warms up a bit?



Compressors have Unloaders, Cheaper ones unload via a schrader in the pressure switch, Commercial/Industrial units have a Centrifugal Unloader.
The short burst of air escaping when the unit shuts down at the pressure cutoff IS the Unloader doing it's job.

Continuous run compressors are different.


Thanks, I always wonder why it sounds like it is releasing a little air when it shuts off but I was referring more to starting one up that had been sitting when it's really cold like single digits. I have a Makita Mac700 and when I bought it a fiend of mine that worked as a building type maintenance guy said to open the valve so it's not trying to build pressure right away when it's really cold until it runs a bit.
 
Originally Posted by LotI
Originally Posted by Chris142
Amsoil makes a compressor oil.

Yup, I've been running their ISO100 in my compressor for years after the initial fill. Seems fine and although pricey, you don't need much in a typical compressor. It's available pretty much anywhere Amsoil is sold. I picked mine up from Weaver off the shelf.

Another vote for Amsoil compressor oil.
 
[Linked Image]


Here's the chart from the manual to my compressor. No idea where IR's oil falls.

The manual specifically says not to run the compressor below 20*F too, which won't happen on a normal basis, but will surely happen as it's going to be used as needed. That said, it looks like I would need a winter and summer fill.
 
One month later and a lot of compressor work and the "look" of the oil in the sight glass still looks brand new. I'm really glad I did a couple of flushes to get those break-in metals out.


......
 
Originally Posted by BigJohn
I just purchased a McGraw air compressor from Harbor Freight a couple days ago. I poured in the oil that was provided, which was nearly .... crystal clear. After only about 10 fill cycles, the oil is already a mid-gray color looking at it through the sight glass. I want to get those break-in metals out and I want to avoid the sump starting to sludge at all.

......

McGraw manual advise to change the oil after first hour of use.
 
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