When retrofitting, can I avoid changing to Alkylbenzene (AB) or Polyolester (POE) by using a lower viscosity mineral oil (MO)?
Reducing oil viscosity to promote oil return, when performing a refrigerant retrofit, is not a recommended practice. Although lowering the oil viscosity might improve its movement throughout the system, it also decreases the oil’s ability to properly lubricate the compressor. This could adversely affect the compressor life. Additionally, lowering the oil viscosity might increase the amount of free oil circulating throughout the system. Even a small increase in the amount of circulating oil can reduce system performance. The best way to ensure proper oil return when performing a retrofit is to use an approved, miscible refrigerant-oil combination. The new oil should have the same viscosity rating as the product it replaces.
