1) Reduces fuel consumption (if FC is higher than before).
2) Reduces engine noise (if it’s noisier then before).
3) Reduces engine vibration (if it vibrates more than before).
4) Reduces white smoke emission (if there are more white smoke then before).
5) Restores power back to engine (by increased oil pressure and better combustibility)
6) Protects new engine or low mileage engine.