{"product_id":"sierra-synthetic-blend-10w30-fcw-4-stroke-outboard-engine-oil-1-gallon-9421cat3","title":"Sierra Synthetic Blend 10W30 FC-W 4-Stroke Outboard Engine Oil, 1 Gallon – 9421CAT3","description":"\u003ch2\u003eSierra Synthetic Blend 10W30 FC-W 4-Stroke Outboard Engine Oil – 1 Gallon | Part #9421CAT3\u003c\/h2\u003e\u003cp\u003eA synthetic-blend 10W30 engine oil formulated specifically for 4-stroke outboard engines, including Mercury 4-cycle outboards that specify 10W30. FC-W and FC-W Cat Compatible certified, this oil meets the NMMA’s requirements for water-cooled 4-stroke marine engines with and without emission catalyst systems — a standard that automotive engine oils do not meet. The gallon jug is the right size for boaters who go through oil regularly or want to keep a full season’s supply on hand.\u003c\/p\u003e\u003ch3\u003eWhy 10W30 FC-W Matters for Outboards\u003c\/h3\u003e\u003cp\u003eMany 4-stroke outboard engines — particularly Mercury and Mariner models — specify 10W30 rather than the 25W40 used in most inboard and sterndrive applications. Using the correct viscosity grade is critical: too heavy an oil reduces cold-start protection and can stress the oil pump; too light an oil may not maintain adequate film strength at operating temperature. The FC-W certification ensures the oil is formulated for the marine environment, not just adapted from an automotive specification.\u003c\/p\u003e\u003ch3\u003eKey Features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNMMA FC-W® Certified \u0026amp; FC-W Cat Compatible\u003c\/strong\u003e — approved for 4-stroke outboard, sterndrive, and inboard engines with and without emission catalyst systems\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApproved for Mercury 4-cycle outboards requiring 10W30\u003c\/strong\u003e — a direct fit for Mercury and Mariner 4-stroke outboard applications\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCatalyst-safe ZDDP technology\u003c\/strong\u003e — prevents phosphorus depletion and extends emission catalyst life\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSynthetic blend base\u003c\/strong\u003e — better thermal stability and oxidation resistance than conventional mineral oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSAE 10W30 multi-grade\u003c\/strong\u003e — good cold-start flow with adequate high-temperature viscosity for outboard use\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSuperior corrosion protection\u003c\/strong\u003e — guards internal engine components against moisture and salt exposure\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIndustry-leading wear protection and deposit control\u003c\/strong\u003e — keeps engine internals clean across the full service interval\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eSpecifications\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eViscosity: SAE 10W30\u003c\/li\u003e\n\u003cli\u003eCertification: NMMA FC-W®, FC-W Cat Compatible\u003c\/li\u003e\n\u003cli\u003eApplication: 4-stroke outboard, sterndrive, and inboard marine engines; specifically approved for Mercury 4-cycle outboards requiring 10W30\u003c\/li\u003e\n\u003cli\u003eSize: 1 US gallon (3.78L)\u003c\/li\u003e\n\u003cli\u003ePart number: 9421CAT3\u003c\/li\u003e\n\u003cli\u003eSold as: Case packs only\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eParts Desk Insights\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eBest use case:\u003c\/strong\u003e This gallon is the go-to format for Mercury 4-stroke outboard owners who do their own oil changes and want to buy a season’s supply at once, or for service shops that stock 10W30 FC-W for Mercury outboard services. The 10W30 grade is specifically required by many Mercury 4-stroke outboards — it is not interchangeable with the 25W40 used in most inboard and sterndrive applications. For a single oil change, the \u003ca href=\"\/products\/11120080027684\"\u003eSierra Synthetic Blend 10W30 FC-W 4-Stroke Outboard Engine Oil, Qt. – 9421CAT2\u003c\/a\u003e is the more economical single-use option. For high-volume shop use, the \u003ca href=\"\/products\/11120076095524\"\u003eSierra 10W30 FC-W 4-Stroke Outboard Oil, 55-Gallon Drum – 94207\u003c\/a\u003e is available. If your engine calls for a non-catalyst-specific 10W30 FC-W oil, see the \u003ca href=\"\/products\/11120075997220\"\u003eSierra 10W30 FC-W 4-Stroke Outboard Oil, Qt. – 94202\u003c\/a\u003e. For the OEM Mercury 10W30 synthetic blend option, see \u003ca href=\"\/products\/8131443359780\"\u003eMercury Synthetic Blend Engine Oil 10W30 – 8M0149203\u003c\/a\u003e.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCompatibility note:\u003c\/strong\u003e Always confirm your engine manufacturer’s oil specification — viscosity grade, FC-W certification level, and any OEM approvals — before ordering. Sold in case packs; confirm case quantity at time of order.\u003c\/p\u003e","brand":"LNS","offers":[{"title":"Default Title","offer_id":51199660261412,"sku":"47-9421CAT3","price":71.69,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0743\/5799\/7604\/files\/47-9421CAT3.jpg?v=1785611255","url":"https:\/\/marisolmarine.com\/products\/sierra-synthetic-blend-10w30-fcw-4-stroke-outboard-engine-oil-1-gallon-9421cat3","provider":"Marisol Marine Company","version":"1.0","type":"link"}