The invention is directed to a method for reducing low speed pre-ignition events in a spark-ignited direct injection internal combustion engine by supplying to the sump a lubricant composition which contains an oil of lubricating viscosity and a boron-containing ashless dispersant. The ashless dispersant may be selected from succinimide compounds prepared from aliphatic or aromatic amines.

Lubricant compositions comprising a base oil, one or more antioxidants selected from a group consisting of N--naphthyl-N-phenylamine antioxidants and diphenylamine antioxidants; and a sulfur-containing additive comprising up to seven carbon atoms exhibit outstanding oxidative stability and non-corrosion properties. The N--naphthyl-N-phenylamine antioxidants plus diphenylamine antioxidants in total may be present from about 0.2 wt % to about 0.8 wt %, based on the total weight of the lubricant composition. The sulfur provided by the sulfur-containing additive may be present from about 50 ppm to about 1000 ppm by weight, based on the total weight of the lubricant composition.

Disclosed are a gear oil composition for automobiles containing at least (A) a base oil, (B) a sulfur-based extreme pressure agent, and (C) a phosphorus-based extreme pressure agent and satisfying specific requirements (i) and (ii), which is excellent in seizing resistance and wear resistance and also in fuel-saving performance, and a lubrication method using the gear oil composition.

Disclosed are a gear oil composition for automobiles containing at least (A) a base oil, (B) a sulfur-based extreme pressure agent, and (C) a phosphorus-based extreme pressure agent and satisfying specific requirements (i) and (ii), which is excellent in seizing resistance and wear resistance and also in fuel-saving performance, and a lubrication method using the gear oil composition.

A method for performing a coiled-tubing process, the method having the steps: performing a coiled-tubing process using a fluid-lubricant composition that includes a sulfur-containing compound, and introducing the fluid-lubricant composition into a subterranean wellbore casing.

The present disclosure relates to lubricating compositions having a stable viscosity upon oxidization through select amounts and relationships of detergent metals and soap contents.

The present disclosure relates to lubricating compositions having a stable viscosity upon oxidization through select amounts and relationships of detergent metals and soap contents.

For efficiently producing a dialkyl polysulfide which is able to be favorably used as an extreme-pressure additive which does not easily corrode the metal surface, and an extreme-pressure additive and lubricating fluid composition including the dialkyl polysulfide, provided is a method for producing dialkyl polysulfide including a first step of reacting an olefin compound (a) represented by General Formula (1): R.sup.1R.sup.2CCHR.sup.3 (where R.sup.1 and R.sup.2 each are an alkyl group, R.sup.3 is a hydrogen atom or an alkyl group, and the total number of carbon atoms of R.sup.1, R.sup.2 and R.sup.3 is 2 to 20) with sulfur in the presence of a hydrogen sulfide to thereby obtain crude dialkyl polysulfide (A), and a second step of reacting the crude dialkyl polysulfide (A) and a sulfide of an alkali metal in a solvent including an alcohol to thereby reduce the number of sulfur atoms in the crude dialkyl polysulfide (A).

For efficiently producing a dialkyl polysulfide which is able to be favorably used as an extreme-pressure additive which does not easily corrode the metal surface, and an extreme-pressure additive and lubricating fluid composition including the dialkyl polysulfide, provided is a method for producing dialkyl polysulfide including a first step of reacting an olefin compound (a) represented by General Formula (1): R.sup.1R.sup.2CCHR.sup.3 (where R.sup.1 and R.sup.2 each are an alkyl group, R.sup.3 is a hydrogen atom or an alkyl group, and the total number of carbon atoms of R.sup.1, R.sup.2 and R.sup.3 is 2 to 20) with sulfur in the presence of a hydrogen sulfide to thereby obtain crude dialkyl polysulfide (A), and a second step of reacting the crude dialkyl polysulfide (A) and a sulfide of an alkali metal in a solvent including an alcohol to thereby reduce the number of sulfur atoms in the crude dialkyl polysulfide (A).

The present disclosure relates to lubricating compositions having a stable viscosity upon oxidization through select amounts and relationships of detergent metals and soap contents.