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A Guide to Marine Lubricants

Quality lubricants are the lifeblood of any marine engine, and you can count on the quality of Mercury Marine Precision Oils and Lubricants to protect your engine when it’s on or off the water.

Equipement et Technologie
A Guide to Marine Lubricants

Your marine engine lives a harsh life. It operates under heavy load at high rpm, which puts tremendous stress on the oil. In the marine environment, corrosion – inside and outside the engine – is a constant threat. When it's not working hard to get you to the fish, or tow you around the lake, or carry you to a distant port, a marine engine is often idle for weeks or months at a time. It's tough duty.

Each Mercury Precision lubricant product has been specially formulated for the unique needs of the marine environment and is rigorously tested to meet our high standards. Other "off the shelf" marine lubricants may meet a basic industry standard. Mercury Precision Oils and Lubricants are designed to exceed those standards. Check your owner's manual, or ask your Mercury dealer for the recommended lubricant products for your marine engine.

Mercury Precision Lubricants 4-Stroke Marine Oil

Mercury Precision Lubricants 4-Stroke Marine OilThe basic standard for four-stroke marine engine oil is the FC-W (four-stroke cycle, water-cooled) certification. Compared with regular motor oil, FC-W oil features more corrosion inhibitors to deal with the marine environment and offers greater resistance to shearing, the permanent loss of viscosity that may lead to greater wear or even catastrophic engine failure. Compared with an auto engine, a marine engine spends much more time at high rpm and under a heavy load, so its oil is more prone to shearing – which is why you should never use automotive oil in a marine engine. Mercury Precision 4-Stroke oils feature a blend of high-quality base stocks and additives formulated specifically for use in most four-stroke outboard, sterndrive and inboard marine engines. This oil is engineered to perform well in legacy engines as well as the latest catalyst-equipped engines.

  • Synthetic Blend 4-Stroke (25W-40) Outboard Oil is specifically formulated for the high-torque/high-rpm duty of supercharged and intercooled Mercury Verado outboards, with a balanced combination of the highest-quality synthetic and mineral base stocks. This oil is first-in-class for all FC-W durability test properties, with industry-leading internal corrosion protection.
  • Synthetic Blend 4-Stroke (25W-50) from Mercury Racing was developed to meet the demands of high-performance and competition engines that get pushed to the limit. Formulated with an advanced additive package, including higher levels of ZDDP to guard against bearing and camshaft wear, this oil maintains its viscosity under long periods of high load/high rpm operation, protects against varnish buildup and sludge formation, and exceeds the rust protection requirements for NMMA certification. It is recommended for most Mercury Racing four-stroke engines and Verado outboards offered before the 2007 model year.
  • Synthetic Blend 4-Stroke (10W-30) Outboard Oil is designed to meet the needs of all four-stroke outboard motors, with industry-leading corrosion protection. A foundation of premium-grade synthetic and mineral-based stocks is formulated with marine-grade additives not required in automotive oils for outstanding resistance to corrosion and excellent shear stability at high rpm.

Mercury Precision Lubricants 2-Stroke Marine Oil

Give your two-stroke some love. This oil exceeds the basic TC-W3 standard and meets manufacturers' recommendations for all two-stroke outboard and personal watercraft engines, in pre-mix or oil-injected applications.

  • Premium 2-Stroke Outboard Oil is formulated to meet the needs of low-to-mid-horsepower outboard engines under general marine operating conditions. This quality TC-W3 oil reduces rust and corrosion of internal components.
  • Premium Plus 2-Stroke Outboard Oil is formulated with a high-concentration marine additive package to meet the needs of high-horsepower two-stroke outboards, including direct fuel-injected engines. This oil far exceeds the performance of the industry TC-W3 standard and Mercury engineering standards. It burns clean to reduce carbon buildup and offers superior lubrication in the most-demanding operating conditions.
  • OptiMax/DFI 2-Stroke Outboard Oil is a synthetic-blend oil specially formulated to meet the needs of Mercury OptiMax and other Direct Fuel Injected (DFI) two-stroke outboard engines. A carefully modified base stock blend with a synthetic additive package minimizes carbon buildup to help maintain engine performance and offers superior lubrication for increased resistance to piston scuffing.

Mercury Precision Lubricants Diesel Engine Oil

This quality, hard-working diesel engine oil contains a higher additive level than standard fleet oils to provide greater protection.

  • Heavy Duty Diesel (15W-40) Engine Oil is formulated to meet the needs of all marine diesel engines, including Mercury MerCruiser D-Tronic models. It provides excellent wear tolerance and shear stability to assure stay-in-grade performance and is designed to protect internal engine components from corrosion and wear. Its formula helps control the formation of sludge and varnish deposits, even in highly stressed applications.

Mercury Precision Lubricants Gear Lube

There is no industry-wide standard for marine gear oils, so it is essential to use products specifically tested for marine applications. Mercury High-Performance Gear Lube has a specialized marine additive package that outperforms automotive gear oil in marine gearcase applications.

  • Premium Gear Lube provides protection against excessive wear even in the presence of water, prevents corrosion and pitting, and helps extend gear life. Recommended for use in lower units of outboards below 75hp.
  • High-Performance Gear Lube provides maximum protection for sterndrive and outboard lower units. An exclusive formula is engineered to extend gear life in extreme conditions, including high-speed and high-horsepower applications. Extreme pressure synthetic additives protect gears from metal-to-metal contact. This gear lube is also specifically formulated to help prevent failures due to water entering the gear housing.

Mercury Marine delivers legendary performance. Genuine Mercury Precision Parts and Lubricants are designed by Mercury engineers to maintain that performance and reliability with uncompromising original-equipment quality and durability. To learn more about Mercury Marine engine and other products, go to

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