What does 4-stroke engine oil mean?

[McSpencer]

Four-stroke engine oil is similar to automotive engine oil. Below is relevant information about four-stroke engine oil: Introduction: The intake valve opens while the exhaust valve closes. The piston moves from top dead center to bottom dead center, increasing the cylinder volume above the piston and creating a vacuum. The pressure inside the cylinder drops below the intake pressure, drawing atomized gasoline through the carburetor or fuel injection system under vacuum suction. Structure: Four-stroke engines belong to reciprocating piston internal combustion engines, which are categorized into three types based on fuel used: gasoline engines, diesel engines, and gas fuel engines. Classification: Reciprocating internal combustion engines using gasoline or diesel fuel are called gasoline engines or diesel engines respectively. Those using natural gas, liquefied petroleum gas, or other gaseous fuels are called gas fuel engines.