Coolant composition, method of operating internal combustion engine using the same, and use of the same

Abstract

A coolant composition includes: a viscosity improving agent; at least one alkali metal compound selected from the group consisting of alkali metal salts and alkali metal hydroxides; and a base composed of water and/or at least one alcohol selected from the group consisting of a monohydric alcohol, a dihydric alcohol, a trihydric alcohol, and a glycol monoalkyl ether, wherein the viscosity improving agent is a compound represented by a formula of RO—(RO)—SOM, where Rrepresents a linear or branched alkyl or alkenyl group having 16 to 24 carbon atoms, Rrepresents an ethylene group or a propylene group, m represents an average addition molar number of RO and a number from 0.5 to 10, and M represents a cation or a hydrogen atom, and a kinetic viscosity of the coolant composition is 8.5 mm/sec or higher at 25° C. and is 2.0 mm/sec or lower at 100° C.