TRIAX Marine Ultra 25W-40 4-Stroke Full Synthetic Engine Oil. Friction Modified Corrosion Inhibited Marine Engine Oil. TRIAX Marine Ultra is a top tier, full synthetic, marine engine oil designed for gasoline powered marine engines. It is built with high performance synthetic base oils and custom modified additive package for outstanding long term engine protection and fuel economy. It contains a friction modifier package plus a state-of-the-art corrosion and rust inhibitor. It actively protects your water-craft engine during periods of intense activity as well as through long storage periods. Designed for NMMA FC-W 4-Stroke outboard engines; use in gasoline-fueled four-stroke inboards, outboards, inboard/outboards, supercharged watercraft engines and personal watercraft. True full synthetic; twice the life of conventional and synthetic blends oil and twice the protection. Unmatched corrosion protection, even in continuous salt water use, including up to two years of storage; excellent stability and viscosity control for long term high temp operation. Friction modified for exceptional wear protection, less heat, better fuel economy, and significantly reduced wear. High film strength and durability under high torque and power output conditions.