A lubricating oil composition for refrigerating machines contains a base oil and an additive in a form of a coumarin compound. When the present lubricating oil composition for refrigerating machines is used in refrigerating equipment such as an open-type automobile air-conditioner, an electric automobile air-conditioner, a gas heat pump, other air-conditioning equipment, a refrigerating machine, a vending machine, a showcase, a water-heating system and a refrigerating/heating system, it is possible to detect the leakage of a refrigerant with a long-lasting stability. Therefore, when an unsaturated chlorofluorocarbon refrigerant with a poor stability is used in the above-listed equipment, the present lubricating oil composition for refrigerating machines is significantly advantageous.

Method for preventing or reducing low speed pre-ignition events in a spark-ignited internal combustion engine is provided. The method includes supplying to the engine a fuel composition comprising a primary additive having a structure given by

##STR00001##

or a salt thereof. R.sub.1 and R.sub.2 are independently H, C.sub.1-C.sub.20 hydrocarbyl group, carboxyl group, ester, amide, ketone, ether, or hydroxyl group. R.sub.3 and R.sub.4 are independently H, C.sub.1-C.sub.20 hydrocarbyl group, carboxyl group, ester, amide, ketone, ether, amino, or hydroxyl group or wherein R.sub.3 and R.sub.4 are part of a cyclic group. R.sub.5 is C.sub.1-C.sub.100 hydrocarbyl group, carboxyl group, ether, or hydroxyl group. Lastly, p is 0 to 2, n is 1 to 5, m is 0 to 2, and p+n+m is less than 6.

A lubricating composition including an oil of lubricating viscosity and at least one of an ortho-oxy substituted diphenylamine compound, a para-oxy substituted diphenylamine compound, or a substituted N-arylchroman-6-amine compound. Methods of using such lubricating compositions are also disclosed.

This disclosure describes a lubricating oil composition. The composition includes a major amount of base oil; and a lubricant additive having the following structure:

##STR00001##

where each R.sup.1 is independently a hydrocarbyl group having 10 to 400 carbons; X is an alkyl, aryl, or heteroaromatic group having 1 to 10 carbons; Y is nitrogen, oxygen, or sulfur; each R.sup.2 is independently a hydrocarbyl group having 1 to 9 carbons; Z is nitrogen, oxygen, or sulfur, and each R.sup.3 is independently a hydrogen or hydrocarbyl group having 1 to 9 carbons with one or more nitrogen, oxygen, or sulfur functionalization, where p is 1 to 3, n is 1 to 20 and m is 0 to 3.

This disclosure describes a gaseous-fueled, low-speed, or medium speed engine lubricating oil composition. The composition includes a major amount of base oil; and a lubricant additive having the following structure:

##STR00001##

where each R.sup.1 is independently a hydrocarbyl group having 10-400 carbons; X is an alkyl, aryl, or heteroaromatic group having 1 to 10 carbons; Y is nitrogen, oxygen, or sulfur; each R.sup.2 is independently a hydrocarbyl group having 1 to 9 carbons; Z is nitrogen, oxygen, or sulfur; and each R.sup.3 is independently a hydrogen or hydrocarbyl group having 1 to 9 carbons with one or more nitrogen, oxygen, or sulfur functionalization, wherein p is 1 to 3, n is 1 to 20 and m is 0 to 3.