AMSOIL Marine Engine Oil is Engineered for Extremes

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AMSOIL Marine ProductsAMSOIL Synthetic Marine Gear Lube
David Hilgendorf
by David Hilgendorf
May 28, 2024

The AMSOIL marine product line is growing again. AMSOIL Marine Engine Oil is now available in one-gallon (3.78-liter) containers for boat engines with larger sumps, covering a wide range of the most popular marine brands and models.

Why it Matters

Engine performance and reliability are keys to spending more time on the water. However, marine engines operate under high loads for extended periods and face constant exposure to wet environments.

The extreme combination of high-rpm engine operation and water invites premature engine wear and corrosion that can reduce engine performance, damage engine components and eventually cause catastrophic engine failure.

On average, a gas-powered marine engine runs at about 5,000 rpm to power a boat at 26 knots (30 mph). In contrast, an automotive engine powering a car 60 mph runs at about 2,000 rpm. The higher temperatures and mechanical stress in marine engines cause inferior oils to break down and lose viscosity faster.

Moisture also causes rust, which acts like sandpaper on engine parts, scouring bearings, the cylinder wall, piston rings and other components, while corrosion eats away at aluminum pistons and other parts.

Protection and Performance

Rust and corrosion protection are not natural features of motor oil. AMSOIL Marine Engine Oil is engineered with potent inhibitors that guard against the damaging effects of rust and corrosion in harsh marine environments to deliver superior protection that maximizes performance and extends your engine life.

  • Go Faster Captain – Do you place a premium on performance? AMSOIL Marine Engine Oil keeps your engine internals clean under the stress of continuous high-rpm and high-temperature operation, so you can run wide-open all day long.
  • Boat More Mate – Nobody enjoys breakdowns or getting stranded offshore. AMSOIL Marine Engine Oil helps keep your engine running, no matter what mother nature throws at you, so you can travel longer and farther, worry free.
  • Stay Salty Sailor – You might enjoy living on the water, but your boat does not. AMSOIL Marine Engine Oil guards against damaging rust and corrosion where the sun doesn’t shine, inside your marine engine.

NMMA Certified

AMSOIL Marine Engine Oil is certified by the National Marine Manufacturers Association (NMMA) for use in four-stroke outboards, inboards, sterndrives (inboard/outboards) and personal watercraft (PWC).

This premium engine oil demonstrates outstanding performance exceeding the NMMA “FC-W” (Four Cycle – Water) catalyst compatible specification requirements.

AMSOIL Marine Engine Oil gives you the peace-of-mind protection of an oil as precisely engineered as your marine engine. It meets or exceeds exacting industry standards and the requirements of marine engine manufacturers, and it is WARRANTY SECURE™ to keep your factory warranty intact.

  • Superior wear and corrosion protection.
  • Maximum performance.


AMSOIL Marine Engine Oil is engineered to provide superior performance and excellent protection against wear, rust and corrosion in high-stress, high-rpm gasoline-powered marine engines. It is available in 10W-30, 10W-40 and 25W-40 viscosities as part of our complete marine product line.

AMSOIL Marine Engine Oil is a high-performance replacement for engine manufacturer-branded lubricants, including those made by Bombardier/BRP, Chevrolet, Ford, Honda, Johnson/Evinrude, Mercury/Mercruiser, Nissan, OMC, Suzuki, Tohatsu, Volvo-Penta and Yamaha.

AMSOIL 10W-30 Synthetic Marine Engine Oil

AMSOIL 10W-40 Synthetic Marine Engine Oil

AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil


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Got Diesel?

Don’t think we’ve left out all you trawler, sailboat, catamaran, yacht, freighter and cruise ship owners. Check out AMSOIL Synthetic 15W-40 Heavy-Duty Diesel Marine Oil to improve the efficiency, performance and longevity of your biggest boats and fleets (available in bulk).

AMSOIL 15W-40 Synthetic Heavy-Duty Diesel Marine Oil is excellent for use with low- or high-sulfur diesel fuels in standard, turbocharged or supercharged engines, including diesels equipped with EGR systems. It is API CI-4+, ACEA E7 and JASO DH-1 certified, for use in the most popular marine diesel engines including those made by Cat,* Cummins,* MAN,* MTU,* Volvo* and Yanmar* (see data sheet for details).

Note: This product is not catalyst compatible and not for use in engines equipped with exhaust aftertreatment systems, including DPF and SCR.

by David Hilgendorf

AMSOIL Technical Writer and 20-year veteran of the motorcycle industry. Enjoys tearing things apart to figure out how they work. If it can’t be repaired, it’s not worth owning.

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AMSOIL Marine ProductsAMSOIL Synthetic Marine Gear Lube