AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil

AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil is certified by the National Marine Manufacturers Association for use in four-stroke outboards, inboards, stern-drives, and personal watercraft. Designed to withstand high-rpm operation and constant water exposure, it effectively prevents engine wear and the formation of rust and corrosion. The oil maintains a consistent lubricating film due to its excellent shear stability, thereby protecting engine components under high stress. Specifically formulated for Mercury and Mercruiser motors, this oil complies with Mercury's guidelines against using full-synthetic oils. It provides outstanding endurance under high stress and high rpm, along with enhanced rust and corrosion protection, making it a top choice for marine engines.

4.9
star rating from
23
total reviews

This AMSOIL product is available in:

Individual Quart Bottles
Cases of 12 Quart Bottles
Individual 55 Gallon Drums
Buy Now
Product Code:

WCMQT-EA

AMSOIL AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil Description

AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil is certified by the National Marine Manufacturers Association for use in four-stroke outboards, inboards, stern-drives, and personal watercraft. Designed to withstand high-rpm operation and constant water exposure, it effectively prevents engine wear and the formation of rust and corrosion. The oil maintains a consistent lubricating film due to its excellent shear stability, thereby protecting engine components under high stress. Specifically formulated for Mercury and Mercruiser motors, this oil complies with Mercury's guidelines against using full-synthetic oils. It provides outstanding endurance under high stress and high rpm, along with enhanced rust and corrosion protection, making it a top choice for marine engines.

25W-40 Synthetic Blend Marine Engine Oil

Engine performance and reliability are key to a successful day fishing or boating. High-rpm operation and constant exposure to water, however, invite engine wear and formation of rust and corrosion, reducing engine performance and life. AMSOIL 25W-40 Synthetic Blend Marine Engine Oil guards against wear while delivering excellent protection against rust and corrosion. It is Warranty Secure® and will not void your marine engine’s warranty.

AMSOIL 25W-40 Synthetic Blend Marine Engine Oil
  • Excellent high-stress, high-rpm endurance
  • Increased rust and corrosion protection

Protects Against Wear

Marine engines operate under high loads and rpm for extended periods. On average, a marine engine powering a boat 30 mph runs at about 5,000 rpm. In contrast, an automotive engine powering a car 60 mph runs at about 2,000 rpm. Higher stress causes traditional automotive oils to break down and lose viscosity. AMSOIL 25W-40 Synthetic Blend Marine Engine Oil is designed with excellent shear stability to deliver a consistent lubricating film. It helps guard engine components from wear for maximum life.

Excellent Anti-Rust Performance

Marine engines are prone to rust and corrosion due to constant exposure to humid, wet environments. Rust on engine parts acts like sandpaper, scouring bearings, the cylinder wall, piston rings and other components, while aluminum pistons and other parts can corrode. Rust and corrosion reduce engine power and eventually cause catastrophic failure.

Good rust protection is not natural to motor oil; it comes only by design. AMSOIL 25W-40 Synthetic Blend Marine Engine Oil is fortified with potent inhibitors that guard against damaging rust and corrosion.

NMMA Certified

AMSOIL 25W-40 Synthetic Blend Marine Engine Oil is certified by the National Marine Manufacturers Association (NMMA) for use in four-stroke outboards, inboards, sterndrives (inboard/outboards) and PWC. This high-quality oil demonstrates outstanding performance and exceeds the NMMA “FC-W” (Four Cycle – Water) specification requirements.

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

TYPICAL TECHNICAL PROPERTIES

25W-40 Synthetic Blend Marine Engine Oil (WCM)

Kinematic Viscosity @ 100°C, cSt (ASTM D445) 16.0
Kinematic Viscosity @ 40°C, cSt (ASTM D445) 139.3
Viscosity Index (ASTM D2270) 121
Flash Point, °C(°f) (ASTM D92) 254(489)
Fire Point, °C(°f) (ASTM D92) 284(543)
Pour Point, °C(°f) (ASTM D97) -31(-24)
NOACK Volatility, % weight loss (g/100g) (ASTM D5800) 3.1
High-Temperature/High-Shear Viscosity, cP (ASTM D5481) 4.8
Total Base Number (TBN) (ASTM D2896) 7.9
Four-Ball Wear Test (ASTM D4172; 40gk, 150°C, 1800 rpm, 1 hr.), Scar, mm 0.40

APPLICATIONS AND RECOMMENDATIONS

Use in gasoline-fueled four-stroke inboards, outboards, inboard/outboards and personal watercraft that require any of the specifications listed below, including those made by Mercury and Mercruiser.

  • API SM
  • NMMA FC-W Catalyst Compatible

TECHNICAL SERVICES

For immediate answers to your technical questions call (715) 399-TECH (8324) between 8 a.m. and 5 p.m. Central time or email tech@amsoil.com.

SERVICE LIFE

Four-stroke outboard motors and personal watercraft: 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 once a year, whichever comes first.

AMSOIL PRODUCT WARRANTY

AMSOIL 25W-40 Synthetic Blend Marine Engine Oil is Warranty Secure®, keeping your factory warranty intact. It is a high-performance replacement for vehicle manufacturer-branded products and is also backed by the AMSOIL Limited Warranty. For complete information visit AMSOIL.com/warranty.aspx.

HEALTH & SAFETY

This product is not expected to cause health concerns when used for the intended application and according to the recommendations in the Safety Data Sheet (SDS). An SDS is available at AMSOIL.com or upon request at 715-392-7101. Keep Out of Reach of Children. Don’t pollute. Return used oil to collection centers.

AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil Reviews

5

star rating

Great product. Excellent customer service

Seems to perform better than oem oil. Fast shipping.

5

star rating

Excellent

Originally I was using too light of an oil and I went to this 25W40 and was very happy with the oil pressure increase and now it doesn’t seem to go through any oil. Big block Chevy

5

star rating

BEEN USING THIS 25W-40 SINCE it has been offered

Great Oil. Have used it on my 1998 7.4 MPI Bravo 3 since it was first offered. Very little oil consumption. No smoke; engine have been running great with good oil pressure at idle at operating temperature.

Read More Reviews

Additional AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil Resources

SAVE 25% As A Preferred Customer

Sign up today for 25% off all AMSOIL products and enjoy other membership perks and rewards as a preferred customer.