525 oil for o-ring lubrication

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525 oil for o-ring lubrication

Postby ajdrake » Tue Nov 06, 2007 8:36 pm

GM recommends using 525 viscosity mineral oil to lubricate o-rings prior to installation. I have visited several stores looking for such a lubricant and I have struck out. Mineral oil, according to wikipedia, is simply a lower viscosity petrolatum, or a runny petroleum jelly. For any chemists out there, is there any reason why petroleum jelly won't work as well as 525 viscosity mineral oil for assembling o-rings?
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Postby cm5400 » Tue Nov 06, 2007 9:08 pm

I would use nylog. You can buy it from the forums host ACSource here
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Re: 525 oil for o-ring lubrication

Postby test specimen » Tue Nov 06, 2007 9:18 pm

ajdrake wrote:GM recommends using 525 viscosity mineral oil to lubricate o-rings prior to installation. I have visited several stores looking for such a lubricant and I have struck out. Mineral oil, according to wikipedia, is simply a lower viscosity petrolatum, or a runny petroleum jelly. For any chemists out there, is there any reason why petroleum jelly won't work as well as 525 viscosity mineral oil for assembling o-rings?


You do not mention what refrigerant you are using. This is kind of important.

Refrigeration mineral oils like the 525 SUS GM oil are specially treated to remove wax and other reactive impurities. Petroleum jelly is not likely to be treated to remove wax.

If you let wax into an R-12 system, it is not a good thing but you can probably live with the consequences as long as you keep the levels of petroleum jelly low.

If you let a lot of wax into a R-134a system, the wax wil drop out of circulation at the expansion device (the first cold spot in the system). The petroleum jelly itself is also likely to drop out of circulation at the expansion device. You probably don't want to live with this situation as it could plug up the system.
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Postby ajdrake » Tue Nov 06, 2007 9:46 pm

It's an R134a system.
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Postby Atomic Punk » Tue Nov 06, 2007 10:02 pm

NYlog is probaly the best, but you will get 10 different answers from 25 different people. I personally still use mineral oil every time and one of the other techs I work with uses dielectric grease, which I would never do, but he has been doing it for years.
You can get mineral oil at any major grocery or drug store. It is not as refined as the mineral oil that R12 systems used to use, but for the small amount needed for o ring lubercation it works just fine, The good news is the last bottle I bought was less than $2 for 20 ozs in the heath and beauty department at Wal mart- that bottle will last for years
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Postby ajdrake » Tue Nov 06, 2007 10:11 pm

Using mineral oil sounds good. Out of curiosity, do you know what its viscosity is?
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Postby Tom Greenleaf » Wed Nov 07, 2007 12:52 am

For just lubing o rings it wouldn't matter. I use 100% pure silicone compound which doesn't say but it is the dielectic grease. Sold at brake specialty places by Dynatex. You should never use enough to get into the system. A smear is it. I like it because it is amazingly corrosion resistant and just will not wash out - also rubber friendly,

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