{"product_id":"sierra-10w-40-fc-w-semi-synthetic-marine-engine-oil-available-in-quart-gallon","title":"Sierra 10W-40 FC-W Semi-Synthetic Outboard Engine Oil - Available in Quart and Gallon","description":"\u003cp\u003eSierra 10W-40 FC-W Semi-Synthetic Engine Oil is formulated for four-stroke marine outboard engines that demand reliable lubrication under sustained high-load, high-rpm running conditions. Marine outboards work harder than automotive engines on average, spending long stretches at high throttle with limited airflow for cooling, so oil needs stronger film strength and heat resistance to prevent wear. This semi-synthetic blend is built to meet those demands, offering strong detergency to keep internal components clean, anti-wear additives to protect pistons, rings, and bearings, and corrosion protection to guard against the moisture that marine engines are constantly exposed to.\u003c\/p\u003e\u003cp\u003eMeeting the FC-W (Four-Cycle Water-cooled) specification set by NMMA for marine engines, this oil is a suitable choice for scheduled oil changes and top-offs on four-stroke outboards calling for a 10W-40 viscosity grade. It is packaged for the marine aftermarket and sold under the Sierra brand, a long-established name in outboard maintenance parts and fluids.\u003c\/p\u003e\u003ch3\u003eSpecifications\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBrand:\u003c\/strong\u003e Sierra\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer Part Number:\u003c\/strong\u003e 18-9551\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eViscosity Grade:\u003c\/strong\u003e 10W-40\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOil Type:\u003c\/strong\u003e Semi-Synthetic\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSpecification:\u003c\/strong\u003e FC-W\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Four-Stroke Marine Outboard Engines\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAvailable Sizes:\u003c\/strong\u003e Quart (946 ml), Gallon (3.785 L)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eSizes \u0026amp; Options\u003c\/h3\u003e\u003cp\u003eThis oil is available in two package sizes: a Quart for smaller top-offs or single oil changes, and a Gallon for engines requiring larger sump capacity or for stocking up ahead of multiple services. Select the size that matches your engine's oil capacity and how many changes you plan to perform, then order the matching SKU below.\u003c\/p\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eWhat viscosity grade is Sierra 18-9551 engine oil?\u003c\/strong\u003e It is a 10W-40 viscosity grade oil, formulated as a semi-synthetic blend meeting the FC-W specification for four-stroke marine outboard engines.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs this oil synthetic or conventional?\u003c\/strong\u003e Sierra 18-9551 10W-40 FC-W oil is a semi-synthetic blend, combining synthetic base stock benefits with conventional oil for four-stroke outboard lubrication.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat does FC-W mean on marine engine oil?\u003c\/strong\u003e FC-W (Four-Cycle Water-cooled) is the NMMA certification standard for oils used in four-stroke, water-cooled marine engines; Sierra 18-9551 10W-40 oil meets this specification.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat sizes does this Sierra oil come in?\u003c\/strong\u003e Sierra 18-9551 10W-40 FC-W semi-synthetic oil is sold in a Quart (946 ml) bottle and a Gallon (3.785 L) container, covering both single top-offs and full oil changes.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow do I know whether to buy the Quart or the Gallon?\u003c\/strong\u003e Choose the Quart if you only need a partial top-off or your outboard's sump takes less than a quart between changes; choose the Gallon if your engine requires more oil per change or you want enough on hand for multiple services of Sierra 18-9551 oil.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs Sierra 18-9551 suitable for all four-stroke outboards?\u003c\/strong\u003e It is intended for four-stroke marine outboard engines specifying a 10W-40 FC-W oil; always confirm your engine manufacturer calls for this viscosity grade and specification before use.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan this oil be used in stern drive or inboard engines?\u003c\/strong\u003e Sierra 18-9551 10W-40 FC-W semi-synthetic oil is formulated for four-stroke marine outboard engines, not stern drive or inboard applications.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes this oil protect against corrosion?\u003c\/strong\u003e Yes, Sierra 18-9551 10W-40 FC-W oil includes corrosion protection additives suited to the moisture exposure common in marine engine environments.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs Sierra 18-9551 a genuine Sierra product?\u003c\/strong\u003e Yes, this 10W-40 FC-W semi-synthetic oil is sold under the Sierra brand as part number 18-9551.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow many quarts are in the gallon container?\u003c\/strong\u003e The Gallon size of Sierra 18-9551 oil holds 3.785 liters, equivalent to 128 fluid ounces, or the equivalent of four quart bottles.\u003c\/p\u003e","brand":"Sierra","offers":[{"title":"Quart","offer_id":48988061597915,"sku":"SIE-18-9551-2","price":10.7,"currency_code":"USD","in_stock":true},{"title":"Gallon","offer_id":48988061630683,"sku":"SIE-18-9551-3","price":42.55,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0839\/7586\/4539\/files\/18-9551-3.png?v=1784938604","url":"https:\/\/www.goodvibesmarina.com\/products\/sierra-10w-40-fc-w-semi-synthetic-marine-engine-oil-available-in-quart-gallon","provider":"Good Vibes Marina","version":"1.0","type":"link"}