A 4-cylinder engine is a type of internal combustion engine that has four cylinders arranged in a line or in a V-shape. Each cylinder contains a piston that moves up and down, creating power by burning fuel and air. This design is popular in many vehicles because it offers a good balance of performance and fuel efficiency. These engines are commonly found in compact cars and some mid-sized vehicles, making them a practical choice for everyday driving. They typically produce less power than larger engines, but advancements in technology have improved their performance and efficiency, making them suitable for a wide range of applications, including sedans and SUVs.