High Vacuum Pump Oil

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What specific synthetic high vacuum pump oil would you recommend for a U.S. General (Harbor Freight #98076) 2.5 CFM Vacuum Pump? No vacuum pump oil information was provided with the product.
 
As far as I can tell most of these smaller "home" unit vacuum pumps take ISO 68 viscosity oil. Robin sells one as does Mobil (Cross reference to Amsoil PCJ PCJ LINK ). Both are petroleum/conventional base oils. The only thing special about these oils, are the low vapor pressure and the dryness.

I have recommended PCI PCI LINK for smaller vacuum pumps and PCK PCK LINK for the bigger pumps in the past with great success, but I hesitate a bit because I just don't know exactly what the supplied HF oil is. I doubt there would be any problem with a 50/50 PCI/PCK (same as PCJ PCJ LINK ) mix as other folks have done in the past with similar vacuum pumps.
 
I just got a reply from HF:

Quote:
The iso is not critical as long as its vacuum pump oil. I recommend the
Yellow Jacket brand, that is what I have used in the past. Vacuum pump
oil is specially designed to absorb air and is non-foaming. Some brands
that I have searched on the internet state iso 100.


With that, I would just get a quart of Amsoil PCK ISO 100 vacuum pump/compressor oil.
 
It's amazing how the vacuum pump manufacturers talk about how critical it is to use the proper high vacuum pump oil and then provide no technical information whatsoever on what the characteristic of that oil should be. This goes for U.S. General (Harbor Freight), Robinair, and MasterCool. I've never seen the likes of it.

Some have said to dump the oil after a month, since it's hygroscopic. Sounds like they are putting this oil in the same league as PAG oil. Any thoughts, Paul?
 
I've serviced a lot of rotary oil filled roughing pumps.

I've never noticed a performance difference from different vacuum oil, including pumps using mineral based oils and those using Fomblin type synthetics.

Oil change frequency depends on what you're pumping. Systems with no process gas (or inert gas) and that aren't open to air I've done annual oil changes on. These were pumps that ran 24/7. I have seen oil filled rotary pumps that were used with a gas mix that required the oil to be changed every 3 days. If it wasn't the oil started polymerizing.

BSW
 
FWIW, I've been running the Robinair oil in the same pump. It is IMO the same thickness as the no-name stuff that came with it, which I ran for only one use then dumped.
 
I just picked up the 3CFM dual stage version of this pump. The manual says 'Use a low viscosity vacuum pump oil (i.e., HFV-46)'. HFV-46 appears to be an oil of Chinese origin not available in small quantities.

After reviewing this thread and the Amsoil literature, I have decided to use Amsoil PCI (ISO 46 compressor oil) in this application.
 
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