Does the density of Refrigerant Oil change a lot when the temperature changes? Please tell me.

From science basics we arrive at the ratio:

Density = Mass / Volume

As this is an inherent property of the fluid it cannot vary, unless the other variable like mass and volume are altered.

In many cases the Specific gravity is used in place of density. From my experience, Specific gravity of some of the commonly used fluids is as follows:

Fuels & Solvents ------>>>>>0.78 to 0.8
Base oils and lubricants-->>0.8 to 0.89
Synthetics -------->>>>>>>>>above 1.0

In the case of most premium Refrigeration oils the base is synthetic, hence thier Specific gravity would be above 1.0. Between Sunoco 3 GS or 4 GS ( I do not know much about this product) as indicated in your query the specific gravity would not be different, unless one of them is a non-synthetic product.

Hussam Adeni

In the ASHRAE 2002 Refrigeration Handbook (Chapter 7) there is published data on pure lubricant viscosity. The data are taken from a paper by Albright and Lawyer from 1959 in the ASHRAE Journal (April):67. You may also find some data from more recent work done by ARTI (Air-Conditioning and Refrigeration Technical Institute) in the MCLR (Material Compatibility and Lubricants Research) program from the mid 1990s when CFC phaseout was done. There are a couple of programs from that research work that used 3GS as a reference fluid to comapre results against when the new POE and PAG lubricants were measured.

4GS is in the chapter and the density versus temperature is a straight line beginnng at appx. 915 kg/m3 at 55 degrees F and dropping to appx. 882 kg/m3 at 150 degrees F. The chapter says all the naphthenic mineral oils have the same slope for the straight line of density versus temperature and are just displaced higher or lower based on their individual density.