Comp oil replacement for automotive SAE20?

[Tizzy]

I’ve got an old Curtis piston compressor that has been in light use (hobby shop) for at least 35 years. I’ve had it for 10 years, and it works like a top.
I just drained out about 2 tablespoons of brown, cruddy, oil/water from the compressor.

The recommended oil is “#20 automotive oil”. So, since I can’t seem to find that, or information regarding its properties, should I use “compressor SAE 20” like Amsoil ….and if not, then what? I’m guessing it’s approximately a 1-2 qrt capacity.

Im hoping that it doesn’t experience a catastrophic failure by introducing a foreign material (clean oil). lol

 

[JavierH19]

I use whatever 0/5w-20 in my Quincy. The compressor doesn't run hard so the oil doesn't thin out, no big need for a thick oil unless it's ran constantly. I prefer it to start splash lubing easier at 30f.

There's nothing wrong with using a detergent oil in a compressor. Just change as always. I always pour that old oil into my truck as It gets dirty but not oxidated. There's no oil filter and it gets dusty. The low heat is no issue for it. But the oil does get a little gritty after a long time.

 

[nwjones18]

My compressor specified the same and I put non detergent 30w in it and haven't had any issues.

 

[Creekside]

You can run ND30 in it without issue. Oreilly's has it, you can get it from many places as QuinCIP(Quincy compressor oil), and IR has one for their piston compressors as well. Quincy heavily cautions against using a detergent oil in their units because supposedly it can cause deposits to form on the reed valves. I've never tried it so I don't know. All of our production compressors get QuinCIP or ND30 from Oreilly's except for the screw compressors.

 

[Lubener]

Straight 30 non detergent will work.

 

[Greasymechtech]

Splurge on the Amsoil

Harborfreight, LowesDepotAce.... have compressor oils, as does many autopart stores.

Motor oil has changed much since that pump was created.

 

[Foxtrot08]

Non-detergents SAE scale, so 20w, 30w, 40w, translates to the ISO scale.

So a SAE 20w converts to a ISO 68.
SAE 30w is ISO 100.
SAE 40w is ISO 150.

I would look for an R&O 68 or a turbine grade 68. If you want to go Synthetic, HPL has one in small quantities. But there are several options for R&O oils in small quantities as well. You typically want to stay away from detergent motor oils in air applications because the blow by can cause build up on the valves. Which, can result in failure and fires.