What does four-stroke engine oil mean?

[VanSarah]

Four-stroke engine oil is similar to automotive engine oil. Introduction: The intake valve opens, the exhaust valve closes, the piston moves from top dead center to bottom dead center, the cylinder volume above the piston increases, creating a vacuum, the pressure inside the cylinder drops below the intake pressure, and under the vacuum suction, gasoline atomized by the carburetor or fuel injection device. Structure: Four-stroke engines belong to reciprocating piston internal combustion engines, which are divided into three categories based on the type of fuel used: gasoline engines, diesel engines, and gas fuel engines. Classification: Reciprocating piston internal combustion engines that use gasoline or diesel as fuel are called gasoline engines or diesel engines, respectively. Reciprocating piston internal combustion engines that use natural gas, liquefied petroleum gas, and other gaseous fuels are called gas fuel engines.