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.