Straight-three engine

A straight-three engine (also called an inline-triple or inline-three) is a three-cylinder piston engine where cylinders are arranged in a line along a common crankshaft. Historically less common than straight-four engines, straight-three engines have been used in small and mid-sized vehicles, motorcycles, and agricultural machinery. Their use has increased since the 2020s as part of a broader industry trend toward smaller, turbocharged engines to meet fuel economy and emissions requirements. By the mid-2020s, they accounted for a small but growing share of new vehicles, after being rare prior to 2020. Compared to straight-four engines, straight-three engines are typically lighter and have fewer moving parts, which can improve efficiency, but have limitations in performance and are prone to vibration, which have largely been overcome by advances in engine and vehicle design.