Disclosed is a method of treating a used hydrocarbon lubricant of ISO Viscosity Grade 46 or higher comprising oxidation products that adversely affect lubricant performance. The hydrocarbon lubricant has a Group II hydrocarbon oil or Group III hydrocarbon oil, optionally one or more lubricant additives, and an amount of varnish. The hydrocarbon lubricant is free of zinc-containing additives. The method comprises adding to the used hydrocarbon lubricant from about 2 percent by weight to about 20 percent by weight of a polyhydroxy polypropylene oxide homopolymer that has a hydroxyl number of from about 12 mg KOH/g to about 58 mg KOH/g as measured according to ASTM D4274.

Heat transfer fluids corresponding to mixtures of at least one hydrogen bond donor and at least one hydrogen bond acceptor are provided. The heat transfer fluids can have an unexpectedly high heat capacity relative to the expected heat capacity based on the heat capacities of the at least one hydrogen bond donor and the at least one hydrogen bond acceptor. In some aspects, the heat transfer fluids can also have a sufficiently high electrical resistivity to be suitable for use in environments such as heat management systems in electric vehicles.

Heat transfer fluids corresponding to mixtures of at least one hydrogen bond donor and at least one hydrogen bond acceptor are provided. The heat transfer fluids can have an unexpectedly high heat capacity relative to the expected heat capacity based on the heat capacities of the at least one hydrogen bond donor and the at least one hydrogen bond acceptor. In some aspects, the heat transfer fluids can also have a sufficiently high electrical resistivity to be suitable for use in environments such as heat management systems in electric vehicles.

Disclosed is the use of a lubricating composition including at least one base oil and at least one polyalkylene glycol (PAG) produced by polymerisation or copolymerisation of alkylene oxides including between 3 and 8 carbon atoms, at least one of which being a butylene oxide, for preventing or reducing pre-ignition in an engine, preferably in a vehicle engine.

Disclosed is the use of a lubricating composition including at least one base oil and at least one polyalkylene glycol (PAG) produced by polymerisation or copolymerisation of alkylene oxides including between 3 and 8 carbon atoms, at least one of which being a butylene oxide, for preventing or reducing pre-ignition in an engine, preferably in a vehicle engine.

The present invention provides a lubricating oil composition comprising: (A) a lubricant base oil including at least one type selected from mineral oil, PAO, and GTL (gas-to-liquid) base oils; (B) a compound having a structure obtained by independently subjecting propylene oxide to addition polymerization with an alcohol or a structure obtained by subjecting a combination of propylene oxide with ethylene oxide and/or butylene oxide to addition polymerization with an alcohol, and being configured so that polyalkylene glycol (PAG) with an oxygen/carbon weight ratio of 0.35 or more and less than 0.45 and/or one or both terminal hydroxyl groups in the polyalkylene glycol (PAG) are blocked; and (C) a fatty acid ester having an oxygen/carbon weight ratio of 0.05 to 0.35.

The present invention provides a lubricating oil composition comprising: (A) a lubricant base oil including at least one type selected from mineral oil, PAO, and GTL (gas-to-liquid) base oils; (B) a compound having a structure obtained by independently subjecting propylene oxide to addition polymerization with an alcohol or a structure obtained by subjecting a combination of propylene oxide with ethylene oxide and/or butylene oxide to addition polymerization with an alcohol, and being configured so that polyalkylene glycol (PAG) with an oxygen/carbon weight ratio of 0.35 or more and less than 0.45 and/or one or both terminal hydroxyl groups in the polyalkylene glycol (PAG) are blocked; and (C) a fatty acid ester having an oxygen/carbon weight ratio of 0.05 to 0.35.

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 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.

The lubricating oil composition includes an oil of lubricating viscosity, one or more compounds containing a carboxylic acid functional group or ester functional group the compound represented by

##STR00001##

each R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 is independently hydrogen or hydrocarbyl group; at least one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is a hydrocarbyl group; and a poly alkylene glycol represented by

##STR00002##

each R.sup.7, R.sup.8, and R.sup.9 is independently hydrogen or hydrocarbyl group and n is from 5 to 1000.