AMSOIL 25w-40 Synthetic Blend Marine Engine Oil

AMSOIL 25W-40 Synthetic Blend Marine Outboard Engine Oil

AMSOIL 25W-40 Synthetic Blend Marine Outboard Engine Oil formulated specifically for Mercury Pro Four Stroke motors that use of 25w-40 Verado synthetic blend oil. API SM

AMSOIL 25W-40 synthetic blend motor Oil exceeds the stringent marine operational requirements of all Mercury’s new 4 and 6 cylinder models. It is formulated for the world’s first and only supercharged and inter-cooled outboard engine made by Mercury. Amsoil 25w-40 Outboard marine blend DOES NOT void any warranty you may have, and you do not have to use Verado Oil in your 4 stroke Mercury. Amsoil 25w-40 synthetic blend as well as ALL of Amsoil’s lubricants are stringently tested to guarantee warranty protection for Mercury and Mariner 4- Stroke outboards.

AMSOIL 25W-40 Formula 4-Stroke® Marine Synthetic blend Motor Oil is a premium-quality synthetic formulation engineered for the harsh operating conditions of marine environments. It withstands the intense mechanical action of continuous, high-rpm operation to deliver superior viscosity protection. Formula 4-Stroke Marine Synthetic Motor Oil is specially fortified with a heavy treatment of advanced additives that protect motors against wear, rust and deposits. It excels in high-horsepower applications and all-day trolling conditions.

Amsoil 25w-40 synthetic blend marine engine oil api SM

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NMMA Certified
AMSOIL 4-Stroke Marine Synthetic Blend Motor Oil 25W-40 is certified by the National Marine Manufacturers Association (NMMA) for use in four-stroke outboard motors. This high-quality oil demonstrates outstanding performance and meets the NMMA FC-W Catalyst Compatible specification requirements.

  • C-W (CAT)® Registration Number: FC-11825T

Superior Protection Against Engine Wear

Marine engines operate under high loads and rpm for extended periods of time, causing traditional automotive oils to break down and lose viscosity. To ensure protection and long-term durability, the NMMA introduced the FC-W Catalyst Compatible standard, which is backward-compatible with the recognized requirements of the FC-W standard. AMSOIL 25W-40 Formula 4-Stroke Marine Synthetic blend Motor Oil meets the FC-W and FC-W Catalyst Compatible shear stability requirements, outperforming competitive oils to deliver a superior lubricating film. Formula 4-Stroke Synthetic Oil contains robust anti-wear additives that further reduce wear in metal-to-metal contact regions.

Excellent Anti-Rust Performance
Marine engines are prone to rust, leading to uncontrolled wear and premature engine failure. Good rust protection is not natural to motor oil; it comes only by design. 25W-40 Formula 4-Stroke Marine Synthetic blend Motor Oil is fortified with a special anti-rust agent, even more than required to pass stringent NMMA FC-W and FC-W Catalyst Compatible anti-rust testing.

AMSOIL 25W-40 Formula 4-Stroke Marine Synthetic blend Motor Oil is recommended for gasoline-fueled four-stroke outboard, inboard, inboard/outboard (I/O) and personal watercraft motors. Use the appropriate viscosity grade where specified in the following:

  • API SM
  • NMMA FC-W Catalyst Compatible

Service Life

  • Four-stroke outboard motors and personal watercraft applications: Due to potential fuel dilution or water contamination, change oil at the engine or watercraft manufacturer-recommended interval.
  • Inboard and I/O applications: Change oil at two times the engine manufacturer recommended interval or one year, whichever comes first.

AMSOIL Formula 4-Stroke 25w-40 Marine Synthetic blend Motor Oil is compatible with conventional and synthetic motor oils. Mixing AMSOIL motor oils with other oils, however, will shorten the oil’s life expectancy and reduce the performance benefits. AMSOIL does not support extended drain intervals where oils have been mixed.

Aftermarket oil additives are not recommended for use with AMSOIL motor oils.

AMSOIL products are backed by a Limited Liability Warranty. For complete information visit

This product is not expected to cause health concerns when used for the intended application and according to the recommendations in the Material Safety Data Sheet (MSDS). USA and Canada (M)SDS are available upon request at 715-392-7101 or on the AMSOIL Website. Keep Out of Reach of Children. Recycle used oil and bottle.

For detailed typical technical properties, download the product data bulletin.

WCT Packaging Information
Code Package Size Unit of Measure Product
WCMQT (WCTQT-EA) Quart Each AMSOIL Marine 25w-40 Synthetic blend Motor Oil
WCMQT (WCTQT-CA) Quart Case of 12 AMSOIL Marine 25w-40 Synthetic blend Motor Oil

Possibly the best synthetic 25-40 blend marine oil out there, in my opinion.