10W-30 (WCT)

Amsoil 4-Stroke 10W-30 Synthetic Marine Engine Oil (WCT)
Data Bulletin 

Product Highlights

For use in 4-stroke gasoline fueled engines in marine applications. Offers unsurpassed wear protection, viscosity stability, low volatility and excellent rust protection. NMMA FC-W approved and “warranty certified”. For use in 4-stroke outboard and marine inboard engines. Also excellent for personal watercraft.

Amsoil Synthetic Marine Engine 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. Synthetic Marine Engine 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.

NMMA Certified

Synthetic Marine Engine Oil 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.

Package Sizes (WCT)

Code Sizes Units
WCTQT (WCTQT-CA) Quart Case of 12
WCT30 (WCT30-EA) 30-Gallon Drum Each
WCT55 (WCT55-EA) 55-Gallon Drum Each
  • NMMA Registration #FC-00358P 10W-30

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 Synthetic Marine Engine 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.

NMMA Catalyst Compatible

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. Synthetic Marine Engine 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 Synthetic Marine Engine 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:

  • Honda®
  • Mercury®
  • Yamaha®
  • Johnson®/Evinrude®
  • Bombardier/BRP®
  • Suzuki®
  • Nissan®
  • Tohatsu®
  • OMC®
  • Volvo Penta®
  • Mercruiser®
  • Chevrolet®
  • Ford®

Note: Amsoil Formula 4-Stroke Marine Synthetic 10W-30 is recommended for use in place of 5W-30 as specified by Honda®.

NMMA Registration: 10W-30 – FC-W (CAT)® Registration Number: FC-00833T

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 Synthetic Marine Engine 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.


Outboard Synthetic 2-Stroke Oil is Warranty Secure, keeping your factory warranty intact. Outboard Synthetic 2-Stroke Oil is a high-performance replacement for vehicle manufacturer-branded products and is also backed by the Amsoil Limited Warranty (G1363). For details, visit www.amsoil.com/warrantysecure.

Amsoil Injector Oil
Kinematic Viscosity @ 100°C, cSt (ASTM D445) 11.8
Kinematic Viscosity @ 40°C, cSt (ASTM D445) 75.6
Viscosity Index (ASTM D2270) 151
Pour Point °C (°F) (ASTM D97) -39 (-38)
Flash Point °C (°F) (ASTM D92) 230 (446)
Four-Ball Wear Test
(ASTM D4172B@40kg,75°C, 1200rpm, 1hr), Scar, mm
Noack Volatility, % weight loss (ASTM D5800) 7.8
High-Temperature/High-Shear Viscosity cP (ASTM D5481) 3.5
Total Base Number 7.9

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