A vapor compression system (20) has: a centrifugal compressor (22) having an inlet (40) and an outlet (42); and an electric motor (28) having a stator (30) and a rotor (32). A plurality of bearings (36) support the rotor. A refrigerant charge comprises a base refrigerant and one or more oils. The one or more oils are present at a total concentration of 80-5000 parts per million (ppm) by weight.

Provided is a lubricating oil composition and methods for controlling one or more of foam tendency and foam stability in such composition using as the oil a mixture of at least two base stocks. The at least two base stocks have a surface tension difference between them such that, when the surface tension difference is greater than 1.0 dynes/cm, then one or more of foam tendency and foam stability are enhanced as compared to foam tendency and foam stability achieved using the base stocks separately and not in the mixture. When the surface tension difference between them is less than 1.0 dynes/cm, then one or more of foam tendency and foam stability are reduced or equivalent as compared to foam tendency and foam stability achieved using the base stocks separately and not in the mixture. Two low-foaming base stocks can produce a significant high foam response that reduces or eliminates the need for pro-foaming additives.

A lubricating fluid suitable for use as a shock absorber fluid is disclosed. The lubricating fluid comprises at least 40 wt %, based upon the weight of the lubricating fluid, of a GTL base oil, has a viscosity index in the range of from 50 to 1000, and a pour point of below 30 C.

Marine gas oil compositions corresponding to fuels and/or fuel blending components are provided that can provide improved friction properties within an engine. Addition of lubricant base stock to a marine gas oil composition can reduce frictional losses within an engine during operation. The benefits in reduction of frictional losses can be observed based on the difference between the indicated mean effective pressure and the actual work delivered by an engine, where the difference corresponds to the frictional mean effective pressure.

Traction fluid additive combination that is usable with any traction fluids base stock is provided. To optimize the traction, low temperature viscosity and shear stability performance, a combination of a polyisobutene and a polymethacrylate may be added to a base oil to obtain a traction fluid with good low temperature viscosity without degrading the shear strength properties of the fluid. To minimize foaming of the traction fluid, a combination of one, two, or more anti-foaming agents may be added to the fluid in addition to a standard additive package.

The present invention relates to compositions for use in refrigeration, air-conditioning, and heat pump systems wherein the composition comprises a tetrafluoropropene and at least one other component. The compositions of the present invention are useful in processes for producing cooling or heat, as heat transfer fluids, foam blowing agents, aerosol propellants, and fire suppression and fire extinguishing agents.

A method for improving wear control of a steel surface lubricated with a lubricating oil through the generation of thick tribofilms. The method includes: (i) using as the lubricating oil a formulated oil, the formulated oil having a composition comprising at least one lubricating oil base stock as a major component; and at least one lubricating oil additive, as a minor component; and (ii) forming a tribofilm on the steel surface. In time-step tribofilm formation measurements of the lubricating oil by a mini-traction machine (MTM) at constant slide-to-roll ratio (SRR), the saturation traction coefficient (f.sub.s), which correlates to tribofilm thickness on the steel surface, is greater than about 0.11. In the method of this disclosure, elongation of timing chain due to wear of chain link pins is less than about 0.07%, as determined by Ford Chain Wear (FCW) test conducted in accordance with ILSAC GF-6 specification. The lubricating oils are useful in internal combustion engines.

Disclosed is a lubricant base stock blend comprising a PAO base stock and an alkylated aromatics (AA) base stock, wherein at least the longer portion of the pendant groups attached to the carbon backbones of the PAO molecules have comparable length to at least the longer portion of the side chain groups attached to the aromatic ring structure of the AA molecules. The comparable lengths of at least the longer portion of the pendant groups and the side chain groups lead to enhanced improvement in oxidation stability of the blend.

A method of performing a cleanup service on an internal combustion engine. The method involves draining used fleet oil from the engine, filling the engine with cleanup oil, draining the cleanup oil after an operation interval, and filling the engine with fresh fleet oil. The method can be performed as a remedial measure for an engine already exhibiting high oil consumption, or as a preventative measure on a healthy engine.

In accordance with the present invention refrigerant compositions are disclosed. The compositions comprise a refrigerant mixture consisting essentially of HFC-32, HFO-1234yf, and CO.sub.2. The compositions are useful as refrigerants in processes to produce cooling and heating, in methods for replacing refrigerant R-410A, and in refrigeration, air conditioning or heat pump systems. These inventive compositions match cooling capacity for R-410A within 10% with GWP less than 400 or less than 300.