Sierra 25W-40 4-Stroke Catalyst Marine Oil This Sierra Premium Blend Engine Oil meets modern recreational 4-stroke engines with or without emission catalyst systems. Sierra 25W-40 is approved for all 4-stroke applications including outboard, sterndrive, and inboard. Features Exceeds all 4-stroke requirements including FC-W and FC-W Cat Compatible Formulated to offer maximum corrosion protection Advanced lubrication for extended engine life and wear protection ZDDP anti-wear additive technology P