Solest 120

Solest 120 is a high-performance synthetic polyolester (POE) lubricant from CPI Fluid Engineering, formulated for commercial and industrial refrigeration and air-conditioning compressors — with a field track record exceeding 25 years. Its ISO VG 120 viscosity sits in the extended-viscosity band that standard grades skip, serving specialized applications — particularly screw compressors — where OEMs specify this intermediate film strength.

Solest lubricants are designed for standard factory fill and OEM retrofitting operations, developed through CPI laboratory studies and OEM compressor bench tests. Against mineral oil, the POE chemistry delivers improved viscosity index, flash and fire points, and pour point — and, critically, the controlled HFC miscibility that ensures oil returns to the compressor instead of logging in the evaporator.

VG 120 exists because VG 100 and VG 170 are both wrong for these machines. This is the single most important thing to know about Solest 120: when a compressor manufacturer calls out an ISO VG 120 polyolester, substituting a VG 100 or a VG 170 because it is on the shelf is not a like-for-like swap. Film thickness at operating temperature, and oil carry-over into the discharge, both change. If the OEM literature names VG 120, order VG 120.

Ordering: Solest is a family of grades, of which 120 is the one we hold. If your compressor manual, oil-separator plate or maintenance schedule names a different Solest grade, send us the exact designation and we will source it — we will not substitute a nearby viscosity on our own judgement.

POE is not interchangeable with other lubricant families. It does not mix with the mineral oils used on R-22 and R-12 plant, with alkylbenzene, or with automotive PAG. A change of family requires a documented flush and oil-change procedure and a fresh filter drier, not a top-up.

Handle it as a moisture-sensitive product. POE absorbs water from the air far faster than mineral oil, and absorbed moisture turns into acid inside a running system — keep the container sealed until charging, use an opened pack promptly, and never leave oil standing open on the bench.

Order Solest 120 when a screw compressor or industrial refrigeration package specifies an ISO VG 120 POE — scheduled oil changes, oil-separator top-ups, post-overhaul refills, and OEM retrofit work where the machine was factory-filled with a Solest grade.