Sierra 10W-30 4-Stroke Conventional Catalyst Marine Oil Sierra 10W-30 4 Stroke Catalyst Engine oil is designed for modern 4-stroke recreational engines with or without emission catalyst systems. Approved for all 4 stroke applications including outboard, inboard, and sterndrive. Exceeds all requirements including FC-W and FC-W Cat compatible. The premium blend provides superior protection against corrosion in harsh marine environments. Anti-wear technology prevents phosphorus depletion to extend