AMSOIL 10W-30 100% SYNTHETIC MARINE ENGINE OIL

AMSOIL 10W-30 100% Synthetic Marine Engine Oil delivers the wear protection, shear stability, and rust resistance that four-stroke marine engines need to survive punishing conditions on the water. Built for anglers, boaters, and anyone running a four-stroke outboard, inboard, or personal watercraft hard, season after season.

Marine engines face a unique combination of challenges that automotive engines never see. Sustained high-rpm operation, saltwater or freshwater exposure, extreme humidity, and long periods of inactivity between seasons all conspire to accelerate wear, promote corrosion, and degrade lesser oils. A standard automotive motor oil simply is not formulated to handle these demands, particularly the constant threat of rust forming inside an engine that may sit idle for months at a time.

FIGHTS VISCOSITY LOSS UNDER HIGH-RPM STRESS
Marine four-strokes routinely operate at or near wide-open throttle for extended periods, whether you're running across the lake to your fishing spot or cruising offshore. That sustained high-rpm load subjects the oil to intense mechanical shear, which can permanently thin out oils with weaker base stocks. AMSOIL 10W-30 Synthetic Marine Engine Oil uses naturally strong synthetic base oils that resist viscosity breakdown. With a High-Temperature/High-Shear viscosity of 3.5 cP (ASTM D5481), it maintains a protective lubricating film even when heat and stress are at their peak. A Four-Ball Wear Test scar diameter of just 0.41 mm (ASTM D4172, 40 kgf, 150°C, 1800 rpm, 1 hour) confirms this oil's ability to limit metal-to-metal contact in critical engine zones, helping preserve compression and power output over the life of the engine.

PROTECTS AGAINST RUST AND CORROSION DURING STORAGE
Rust protection does not come naturally to motor oil. It requires deliberate formulation. AMSOIL Synthetic Marine Engine Oil is fortified with potent rust and corrosion inhibitors designed specifically for the marine environment. This matters most during the off-season, when engines sit idle in damp storage conditions for weeks or months. Internal engine surfaces are vulnerable to moisture-driven corrosion during these periods, and conventional marine oils often fall short. AMSOIL's formulation provides active protection during use and throughout long-term storage, so your Yamaha outboard, Mercury four-stroke, or MerCruiser inboard is ready to fire up clean when spring arrives.

LOW VOLATILITY FOR REDUCED OIL CONSUMPTION
High operating temperatures in marine engines can cause lighter oil molecules to evaporate, leading to increased oil consumption and thickened remaining oil. AMSOIL 10W-30 Marine Engine Oil posts a Noack Volatility of just 7.8% weight loss (ASTM D5800), meaning it resists burn-off and stays in the crankcase where it belongs. A flash point of 230°C (446°F) per ASTM D92 further demonstrates the thermal stability of this formulation.

COLD-WEATHER PERFORMANCE AND VISCOSITY RANGE
Early-season launches and cold morning startups are no problem. With a pour point of -39°C (-38°F), this oil flows readily at low temperatures, reducing dry-start wear on engine bearings and cylinder walls. The viscosity index of 151 (ASTM D2270) indicates excellent performance across a wide temperature range, maintaining appropriate film strength when hot without becoming excessively thick when cold.

NMMA FC-W CATALYST COMPATIBLE CERTIFIED
AMSOIL 10W-30 Synthetic Marine Engine Oil carries NMMA FC-W Catalyst Compatible certification (Registration Number FC-00833T), which is backward-compatible with the standard FC-W specification. This certification means it has been independently tested and approved by the National Marine Manufacturers Association for use in four-stroke outboard motors, including catalyst-equipped models. It also meets API SM and JASO MA specifications.

SPECIFICATIONS AND COMPATIBILITY
This oil is designed for use in gasoline-fueled four-stroke inboards, outboards, inboard/outboard engines, supercharged watercraft engines, and personal watercraft. Compatible applications include engines made by Honda, Mercury, Yamaha, Johnson/Evinrude, Bombardier/BRP, Suzuki, Nissan, Tohatsu, OMC, Volvo-Penta, MerCruiser, Chevrolet, and Ford marine engines. It is compatible with other synthetic and conventional motor oils, though mixing will reduce the performance benefits and service life of the AMSOIL product. Aftermarket oil additives are not recommended.

AMSOIL 10W-30 Synthetic Marine Engine Oil is Warranty Secure, keeping your factory warranty intact as a high-performance replacement for manufacturer-branded products.

SERVICE LIFE
For four-stroke outboard motors and personal watercraft, change oil at the engine or watercraft manufacturer-recommended interval due to the potential for fuel dilution or water contamination. For inboard and I/O applications, change oil at two times the engine manufacturer-recommended interval or one year, whichever comes first.