Specially engineered for marine applications. Durable formulation protects in severe conditions, from all-day trolling to high-rpm operation. Heavily fortified with advanced additives designed to prevent deposits, rust and corrosion. Use in gasoline-fueled four-stroke inboards, outboards, inboard/outboards and personal watercraft, including those made by Honda,* Mercury,* Yamaha,* Johnson/Evinrude,* Bombardier/BRP,* Suzuki,* Nissan,* Tohatsu,* OMC,* Volvo-Penta,* Mercruiser,* Chevrolet* and Ford.*
Naturally strong base oils resist viscosity loss due to mechanical shear.
Develops a tough lubricating film that protects engine parts, even in high-heat, high-rpm conditions that break down other oils.
Contains robust anti-wear additives that further reduce wear in metal-to-metal contact regions, guarding against compression loss for maximum power and engine life.
EXCELLENT ANTI-RUST PERFORMANCE
Fortified with potent inhibitors that guard against damaging rust and corrosion.
Protects engines during use and during inactivity or long-term storage.
NMMA CERTIFIED
Certified by the National Marine Manufacturers Association (NMMA) for use in four-stroke outboard motors.
Demonstrates outstanding performance and meets the requirements of the NMMA FC-W Catalyst Compatible specification, which is backward-compatible with the FC-W specification.
*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use.
I HAVE CHANGED ALL OF MY FLUIDS OVER TO AMSOIL. THE BOAT ENGINE SEEMS TO FIRE UP QUICKER AND RUN MORE SMOOTHLY WITH THE AMSOIL MARINE 10-40. MANY FELLOW BIG MOTOR PEOPLE I KNOW STILL USE 20-50 OR STRAIGHT 50 IN THE HEAT ON LAKE MOHAVE AND HAVASU, BUT I HAVE FOUND IM STILL CONSISTENTLY AT 50 PSI OIL PRESSURE AT OPERATING TEMP AND AM HAPPY WITH THAT
Excellent oil characteristics that prolong engine life during hot summer months and cold winter storage. love this oil.
Bottom Line
Yes, I would recommend this to a friend.
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5 star rating
Great oil
By 
DREW, 
a 
Verified Buyer 
on 
January 27, 2025
I have run this oil in my 4 stroke Suzuki DF50 outboard since I took the break in oil out. This motor gets run HARD either running wide open up the Missouri River or idling for long periods in no wake areas and this oil shows no signs of giving up between 100hr service intervals. The inside of this motor is spotless and I don’t worry about corrosion even during longer term storage.
My Yamaha F115 outboard runs smoothly and efficiently. Been using this oil for the last 5 years, highly recommended!
Bottom Line
Yes, I would recommend this to a friend.
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5 star rating
Engine
By 
ANTHONY, 
a 
Verified Buyer 
from 
Port Colborne Ontario Canada 
on 
November 13, 2024
I've been using this oil in my 75hp Yamaha for 10 Plus years
I'm a charter boat for fishing which means I depend on my motor running at peak performance
This motor idles for 2-6 hours per trip. I inspect my spark plugs regularly and have never had an issue with fouling plugs. when i go to full throttle she never lets me down. I change its oil once a year and like what I see.
Great oil as always. However, got a new motor this year and the look up guide sucks. Hasn’t been changed in years. Just refer to your owners manual for correct application.
Good stuff! Got it in my cars, trucks (diesel & gas), tractors, mowers, saws, skid steer, backhoe, boat, bikes, & bedrooms (squeaky hinges/springs ya know). AMSOIL hasn't let me down in 25 years. Proud, proud, proud!
Bottom Line
Yes, I would recommend this to a friend.
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5 star rating
Suzuki 150hp & Suzuki 9.9hp
By 
Too Tall, 
a 
Verified Buyer 
from 
Port Angeles, WA. 
on 
April 24, 2024
Been using Amsoil Marine Oil since motors were new, 2009. Have had zero engine problems. Also use lower unit oil, filters and grease.
Quality products
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