Lucas Oil 25W-40 Marine Engine Oil FC-W – 5 qt Stern Drive/Inboard, Synthetic-Enriched Protection

Lucas Oil SAE 25W-40 Stern Drive Inboard Marine Oil FC-W is a heavy-duty 4-stroke marine engine oil formulated to protect inboard and stern drive engines, support catalytic-system longevity, and resist rust during storage.

Built for stern drives, inboards and compatible 4-stroke outboards, this Lucas Oil marine formulation meets or exceeds NMMA FC-W performance and aligns with MERCRUISER® sterndrive requirements. It combines a robust viscosity profile with synthetic-enriched additives to protect moving parts from wear, inhibit corrosion and help preserve catalyst performance in newer engines equipped with emission control systems.

How does this oil protect engines during heavy use?

The 25W-40 viscosity provides a stable lubricating film at operating temperatures, reducing metal-to-metal contact under load. Additives in the formula condition component surfaces, lowering wear rates and extending component life in demanding marine environments.

• Thicker high-temperature film for load-bearing protection
• Wear-inhibiting additives that reduce friction on bearings and gears
• Formulated to meet MERCRUISER® stern drive specifications

Will this oil help engines with catalytic converters?

This product is engineered to increase catalyst life in newer inboards that use catalytic converters by meeting NMMA FC-W standards designed for emission-sensitive engines. It balances detergency and additive chemistry to minimize catalyst-fouling deposits while maintaining engine cleanliness.

• Meets or exceeds NMMA® FC-W (CAT) performance
• Lower propensity for ash and deposit formation that can harm catalysts
• Suitable for emission-controlled marine engines when FC-W is specified

Can I use Lucas 25W-40 marine oil for storage or seasonal layup?

The formula includes synthetic-enriched corrosion inhibitors that cling to metal surfaces and help guard against rust and moisture during idle periods or long storage. Proper lubrication and corrosion protection make it a good choice if your boat spends months unused between seasons.

• Synthetic additives form a protective coating on internal parts
• Inhibits rust and corrosion during long storage intervals
• Recommended when winterizing or storing vessels for extended periods

Is this oil compatible with other marine and automotive engines?

Lucas 25W-40 FC-W is primarily formulated for marine stern drives and inboards, but it also meets API SM performance levels, meaning it can be used in certain automotive applications where API SM oils are called for. Always consult your engine or vehicle manufacturer’s recommendations before switching oil types.

• Meets API SM thresholds for cross-compatibility in some autos
• Suitable for select 4-stroke outboards and personal watercraft where specified
• Follow manufacturer guidance for viscosity and spec requirements

Who is this for: Boaters, marinas and marine technicians who maintain stern drive and inboard engines—especially vessels with catalytic converters—will benefit from this Lucas Oil 25W-40 formulation. It’s a practical pick for owners seeking strong wear protection, storage corrosion resistance and compatibility with FC-W required systems. If your engine manual specifies NMMA FC-W or a 25W-40 marine oil, this product provides a concentrated, quart-sized option from a recognized marine lubricant brand.