Composition and method for preventing or reducing engine knock and pre-ignition in high compression spark ignition engines

A method for preventing or reducing engine knock or pre-ignition in a high compression spark ignition engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil including a Group I, Group II, Group III, Group IV, Group V base oil, or mixtures thereof, said formulated oil having a composition comprising at least one branched polyol ester,

• wherein the at least one branched polyol ester includes from 42% to 45% of the carbons in the form of methyl groups,
• wherein the at least one branched polyol ester is a mono-pentaerythritol ester of branched mono-carboxylic acids base oil or a di-pentaerythritol ester of branched mono-carboxylic acids base oil,
• wherein the branched mono-carboxylic acids are selected from the group consisting of 2,2-dimethyl propionic acid (neopentanoic acid), neoheptanoic acid, iso-hexanoic acid, 3,5,5-trimethyl hexanoic acid (TMH), isoheptanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, and mixtures thereof,
• wherein the at least one branched polyol ester is present in an amount of from 90 to 95 weight percent, based on the total weight of the formulated oil, and
• wherein the at least one branched polyol ester, when 1% of which is added to isooctane, maintains at least 100% of the isooctane ignition or combustion delays as determined using the equipment and test conditions of ASTM D7668.