This invention proposes a lubricating oil composition for a four-
stroke engine specifically designed for unmanned aerial vehicles (UAVs) and its preparation method. The lubricating oil composition for a four-
stroke engine of this invention comprises the following components: (A) a
nitrogen-containing organoboron compound; (B) an
alkyl diphenylamine; (C)
polyisobutylene succinimide; (D) sulfonates and / or sulfurized
alkylphenol salts; (E)
zinc dialkyl dithiophosphate; (F) dialkyl
dithiocarbamate; (G)
polymethyl methacrylate; and (H) a
base oil in a major amount. The structure of the
nitrogen-containing organoboron compound is shown in formula (I) and / or formula (II), with the definitions of each group provided in the specification. The lubricating oil composition for a four-
stroke UAV engine of this invention exhibits excellent extreme pressure anti-wear, anti-oxidation, and detergency properties, effectively suppressing the increased wear caused by the high power-to-weight ratio and harsh
lubrication conditions of four-stroke UAV engines.