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.*
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Product data sheets
View, download, or save a copy of the Product Data Sheet or Safety Data Sheet for AMSOIL 10W-30 100% Synthetic Marine Engine Oil.
AMSOIL 10W-30 100% Synthetic Marine Engine Oil is a premium synthetic 4-stroke formulation built for gasoline-fueled inboards, outboards, sterndrives, supercharged watercraft, and personal watercraft that call for an SAE 10W-30 viscosity grade. The formulation carries NMMA FC-W Catalyst Compatible certification (registration FC-00833T) and meets API SM and JASO MA, which fits owners of Mercury, Yamaha, Honda, Volvo Penta, Mercruiser and similar 4-stroke gasoline marine engines that specify 10W-30.
Engineered for high-rpm, high-heat marine operation
Marine engines spend long stretches at sustained high rpm under load, which is exactly the duty cycle that breaks down ordinary motor oil. The naturally strong synthetic base oils in this formulation resist viscosity loss from mechanical shear and develop a tough lubricating film that holds up in high-heat, high-rpm conditions. Robust anti-wear additives further reduce wear in metal-to-metal contact regions, guarding against compression loss for sustained power and engine life.
Four-ball wear testing per ASTM D4172 at 40 kgf, 150 degrees C and 1,800 rpm produced a 0.41 mm scar diameter, and a high-temperature/high-shear viscosity of 3.5 cP per ASTM D5481 supports stable oil film thickness on bearings and ring lands at wide-open throttle.
Excellent rust and corrosion protection
Rust protection is not a natural property of motor oil; it has to be engineered in. This formula is fortified with potent inhibitors that guard internal engine surfaces against damaging rust and corrosion. Protection holds during seasonal storage and any extended period of inactivity, which matters for any 4-stroke marine engine pulled from the water for winter or left unused for weeks between trips.
NMMA FC-W Catalyst Compatible certified
The 10W-30 grade is certified by the National Marine Manufacturers Association (NMMA) for use in four-stroke outboard motors and carries the FC-W Catalyst Compatible registration FC-00833T. The Catalyst Compatible specification is backward-compatible with the original FC-W requirement, so the same bottle covers older 4-stroke outboards that call for FC-W and newer engines fitted with three-way catalyst exhaust aftertreatment.
Multi-OEM 4-stroke gasoline coverage
The 10W-30 grade is approved for use in gasoline-fueled four-stroke inboards, outboards, inboard/outboards (sterndrives), supercharged watercraft engines and personal watercraft, including units built by Honda, Mercury, Yamaha, Johnson/Evinrude, Bombardier/BRP, Suzuki, Nissan, Tohatsu, OMC, Volvo Penta, Mercruiser, Chevrolet, and Ford. The formulation also meets API SM and JASO MA, which clears it for shared-sump 4-stroke applications that require a wet-clutch-compatible motor oil.
Low volatility and a wide operating range
The synthetic base oils hold NOACK volatility to 7.8 percent weight loss by ASTM D5800, which limits evaporative losses during sustained high-temperature operation and helps preserve viscosity between oil changes. A viscosity index of 151 by ASTM D2270, a pour point of -39 degrees C and a flash point of 230 degrees C round out a wide operating range suited to spring through fall boating and any climate where the engine sees real cold-start use.
Recommended applications and service intervals
The 10W-30 grade is intended for owners whose 4-stroke gasoline marine engine specifies an SAE 10W-30 viscosity. Common fits include many Volvo Penta gasoline sterndrives, smaller Mercury and Mercruiser 4-stroke engines, certain Yamaha and Honda 4-stroke outboards and a range of Indmar, PCM, and Crusader inboards that call for a 10W-30 marine oil. For applications that specify 25W-40, switch to the AMSOIL 25W-40 marine grade. Confirm the correct viscosity for a specific boat with the AMSOIL vehicle lookup guide before ordering.
Four-stroke outboard motors and personal watercraft applications: change oil at the engine or watercraft manufacturer-recommended interval due to potential fuel dilution or water contamination.
Inboard and I/O applications: change oil at two times the engine manufacturer-recommended interval or one year, whichever comes first.
Not intended for 2-stroke outboards or diesel marine engines; those engines require a TC-W3 or marine diesel formulation.
Outside the US and Canada, follow the engine manufacturer service schedule and any local marine emissions or registration requirements.
Pair the oil change with a quality marine oil filter. The 10W-30 grade is compatible with other synthetic and conventional motor oils, but mixing reduces the performance benefits and shortens service life, so an extended drain interval after any mix-in is not supported. Aftermarket oil additives are not recommended for use with this formulation.
Typical technical properties
Property
Value
Kinematic viscosity at 100 degrees C, cSt (ASTM D445)
11.8
Kinematic viscosity at 40 degrees C, cSt (ASTM D445)
Four-ball wear scar, mm (ASTM D4172 at 40 kgf, 150 degrees C, 1,800 rpm, 1 hr)
0.41
NOACK volatility, percent weight loss (ASTM D5800)
7.8
Total base number
7.9
Order AMSOIL 10W-30 100% Synthetic Marine Engine Oil
Available sizes include the quart bottle (WCTQT-EA), case of 12 quarts (WCTQT-CA), one-gallon jug (WCT1G-EA), case of four one-gallon jugs (WCT1G-CA) and the 55-gallon drum (WCT55-EA) for marina, fleet, and service-shop use. The product is Warranty Secure under the AMSOIL Limited Warranty, which keeps the engine factory warranty intact when this oil is used in line with the manufacturer service schedule. Match the 10W-30 to a specific boat with the AMSOIL vehicle lookup guide, compare it across the broader AMSOIL motor oil range in the AMSOIL motor oil guide, then Order Now.
I buy this oil for my Yamaha f150. This kit is cheaper than the Yamaha oil change kit with a filter. Also it’s fully synthetic which I prefer.
By Kane from NE Florida on July 15, 2026.
Would recommend this to a friend.
....only the Best....
....Amsoil Marine oil is the only choice for me...10/30 is a perfect choice for my Boat....I've been a 50+ year Customer of Amsoil products....only the Best...thankyou Amsoil....
Is marine engine oil different from automotive motor oil?
Yes. Marine 4-stroke engines run at sustained high rpm under load and spend much of their service life in humid air, so the oil needs higher film strength at temperature and a stronger rust and corrosion package than a typical passenger-car oil. AMSOIL 10W-30 100% Synthetic Marine Engine Oil carries NMMA FC-W Catalyst Compatible certification (FC-00833T), which is the marine industry battery of wear, oxidation, corrosion, and emulsion tests; an off-the-shelf automotive 10W-30 is not built or qualified against those tests.
How often should the oil be changed in a 4-stroke marine engine?
For four-stroke outboards and personal watercraft, change the oil at the engine or watercraft manufacturer recommended interval; the practical limit on marine outboards is fuel dilution and water contamination, not the oil itself. For inboards and inboard/outboards, the formulation supports up to two times the engine manufacturer recommended drain interval or one year, whichever comes first.
Can a different viscosity be used if the engine calls for 10W-30 marine oil?
No. The correct viscosity is the one printed in the engine manual. Engines specified for 10W-30 should run a 10W-30 marine oil; substituting a 25W-40 in an engine designed for 10W-30, or the reverse, changes oil flow at start-up and film thickness at operating temperature in ways the engine manufacturer did not validate.
Does NMMA FC-W Catalyst Compatible matter for 4-stroke marine engines?
Yes. FC-W Catalyst Compatible is the NMMA specification for oils used in 4-stroke outboards fitted with catalyst-equipped exhaust aftertreatment, and it remains backward-compatible with the older FC-W requirement. The 10W-30 grade carries registration FC-00833T, so the same product covers older FC-W engines and newer catalyst-equipped 4-stroke outboards.
Is this oil suitable for supercharged marine engines and PWC?
Yes. Approved applications include gasoline-fueled four-stroke inboards, outboards, inboard/outboards, supercharged watercraft engines and personal watercraft, including units made by Honda, Mercury, Yamaha, Johnson/Evinrude, Bombardier/BRP, Suzuki, Nissan, Tohatsu, OMC, Volvo Penta, Mercruiser, Chevrolet, and Ford. The JASO MA rating also covers the shared-sump PWC platforms that route engine oil through a wet clutch.
Does running AMSOIL synthetic oil void the boat factory warranty?
No. Using an AMSOIL synthetic lubricant that meets the engine manufacturer specification does not void the factory warranty under United States warranty law, and this oil is covered separately by the AMSOIL Limited Warranty. Keep service records that show the correct viscosity grade was used at the correct interval.
