The air filter, code P51321-03, is a fundamental component in the MAN L21/31 engine’s intake system, responsible for preventing dust, debris, and other airborne contaminants from entering the combustion chamber. By ensuring a continuous supply of clean air, it protects internal engine parts from wear and maintains efficient combustion. Especially in harsh or marine environments, a high-quality air filter extends engine life, supports consistent performance, and contributes to lower emissions and optimal fuel usage.