The invention relates to an engine
oil additive for a small
gasoline engine. The engine
oil additive is prepared from the following components in parts by weight: 0.1-10 parts of a composite detergent, 0.1-4 parts of an ashless dispersant, 0.1-2.5 parts of an oxidation and
corrosion inhibitor, 0.05-1.0 part of an
antioxidant, 0.001-1.5 parts of an organic
molybdenum additive and 0.001-0.01 parts of an anti-
foaming agent, wherein the composite detergent is prepared from two or three of
sulfonate, salicylate and sulfurized
alkylphenol salt by mixing. The invention further relates to engine oil composition containing the additive. The provided additive and composition have good high-temperature detergency,
oil sludge dispersity and
oxidation resistance, low generation probability of high-temperature deposit, small
evaporation loss and lower
oil consumption, can slow down the formation trend of engine oil deposit of the small
gasoline engine, and enables engine
oil sludge formed at low temperature to be suspended in engine oil, so that starting abrasion is effectively reduced.