Disclosed are refrigerants comprising at least about 97% by weight of a blend of three compounds, said blend consisting of:

from about 38% by weight to about 48% by weight difluoromethane (HFC-32),
from about 6% by weight to about 12% by weight pentafluoroethane (HFC-125),
from about 33% by weight to about 41% by weight trifluoroiodomethane (CF.sub.3I) and
from about 2% by weight to about 16% by weight 2,3,3,3-tetrafluoropropene (HFO-1234yf)
wherein the percentages are based on the total weight of the three compounds in the blend, and methods and systems which use same.

Disclosed are refrigerants comprising at least about 97% by weight of a blend of three compounds, said blend consisting of: from about 40% by weight to about 49% by weight difluoromethane (HFC-32), from about 6% by weight to about 12% by weight pentafluoroethane (HFC-125), from about 33% by weight to about 40% by weight trifluoroiodomethane (CF.sub.3I); and from about 2% by weight to about 12% by weight of trans 1,3,3,3-tetrafluoropropene (trans HFO-1234ze), wherein the percentages are based on the total weight of the three compounds in the blend, and systems and method using same.

Provided are an ester of isotridecanoic acid and pentaerythritol, etc., wherein (i) the kinematic viscosity at 40 C. is in the range of 80-140 mm.sup.2/sec. and (ii) the number of terminal methyl groups per molecule of isotridecanoic acid in the isotridecanoic acid obtained by .sup.1H-NMR measurement is in the range of 2.6-3.4 on average.

Provided are both a grease composition for an electric power steering device and an electric power steering device. The grease composition can keep a sufficiently low coefficient of friction in a sliding area between a steel and a resin over a long period, is less susceptible to being removed from the sliding area, does not cause break down of an oil film, and thus can minimize the occurrence of stick-slips. A grease composition for an electric power steering device, containing a synthetic hydrocarbon oil which exhibits a density of 0.75 to 0.95 g/cm.sup.3 at 15 C., a saturated aliphatic amide compound, boron nitride, a glycerin fatty acid partial ester, and a metal soap-based thickener; and an electric power steering device using the grease composition.

A lubricating oil composition according to one embodiment of the present invention contains an oxygen-containing synthetic base oil having an oxygen content (A) of from 15 to 40 mass % and a kinetic viscosity at 100 C. of from 0.5 to 50 mm.sup.2/s, and a viscosity index improver that is an oxygen-containing compound having an oxygen content (B) of from 15 to 40 mass % and a kinetic viscosity at 100 C. of 11,000 mm.sup.2/s or more, a mass ratio of the oxygen-containing synthetic base oil and the viscosity index improver being from 99.5:0.5 to 75:25, and a ratio (A/B) of the oxygen content (A) of the oxygen-containing synthetic base oil to the oxygen content (B) of the viscosity index improver being in a range of from 0.5 to 2.

A ball bearing according to the present invention is filled with a grease composition. The grease composition contains a synthetic oil other than a synthetic hydrocarbon oil, a synthetic hydrocarbon oil, a mineral oil, and a urea compound. The synthetic oil other than the synthetic hydrocarbon oil is contained in an amount of 10% by mass or more and 60% by mass or less when the total of the synthetic oil other than the synthetic hydrocarbon oil, the synthetic hydrocarbon oil and the mineral oil is taken as 100% by mass.

A blend for lubricating a surface includes a lubricant and a polyepoxide terpolymer additive mixed with the lubricant. The polyepoxide terpolymer additive includes a first block having a group R1, a second block having a group R2, and a third block having a group R3. Group R1 includes C.sub.4H.sub.9 or C.sub.6H.sub.13, group R2 includes CH.sub.3, and group R3 includes C.sub.6H.sub.5.

A lithium salt thickener that enhances thermal stability at high temperature and operability at low temperature, and a grease composition including the same, is provided.

Provided are a water-soluble metalworking oil agent (cutting oil agent or grinding oil agent) and a metalworking liquid, each of which has excellent cutting machining performance or grinding machining performance of aluminum or aluminum alloys, hardly causes rotting deterioration, and has excellent emulsion dispersion stability and stability of undiluted liquid, by containing specified components (A) to (E) as essential components without containing a machinability-improving agent with a high environmental load, such as chlorine, sulfur, and phosphorus. Provided is also a metalworking method using the same.

The lubricating base oil of the present invention comprises an ester synthesized from: a first component that is at least one selected from polyhydric alcohols having 2 to 4 hydroxyl groups; a second component that is at least one selected from polybasic acids having 6 to 12 carbon atoms; and a third component that is at least one selected from monohydric alcohols having 4 to 18 carbon atoms and monocarboxylic acids having 2 to 12 carbon atoms. In addition, the refrigerating machine oil and the working fluid composition for a refrigerating machine of the present invention each comprise the above lubricating base oil.