Lubricants

Your Mercury Marine® engine needs the protection that only quality marine lubricants can provide, the kind of protection your engine simply will not get from a lubricant designed for use in automobile engines. Mercury Marine has developed a complete line of Mercury Precision Lubricants®, each a premium product designed to protect your Mercury® engine when it is on and off the water.

Why use marine lubricants instead of automotive lubricants?

Harsh duty

A marine engine is designed to operate for hours at high rpms and under heavy load. This torturous duty requires special lubricants, which is why you should never use automotive oil in a marine engine. The extended high-rpm operation that a marine engine endures can shear (or split) inferior additive molecules, leading to permanent loss of viscosity. Mercury formulates its 4-stroke marine engine oil products with additives specifically designed to offer powerful shear resistance and viscosity retention – vital for long-term marine engine performance.

A cool operator

Marine engines operate at much lower temperatures than automotive engines. Mercury Precision Lubricants engine oils are formulated to provide outstanding protection against wear and corrosion at lower temperatures than automotive oil.

Tough neighbourhood

In the marine environment, corrosion – inside and outside the engine – is a constant threat. A marine engine often sits idle for weeks or months at a time, which creates an opportunity for condensation to collect inside the engine. Mercury Precision Lubricants oil products contain specific anti-corrosion inhibitors, which simply are not present in automotive engine oil, formulated to protect your engine under these conditions.

Mercury lubricants exceed industry standards

Marine engine manufacturers and the National Marine Manufacturers Association® (NMMA®) worked together to develop basic standards for engine oil specifically designed for the unique marine environment. Consumers should look for the distinctive trademark to identify marine engine oil that meets this standard. While “off the shelf” marine lubricants may meet this basic industry standard, Mercury Precision Lubricants are designed to exceed those standards, often by a significant margin.

Essential oil changes

Keeping up with scheduled oil changes is important for maintaining the peak performance of your hard-working engine.

Check the maintenance schedule in your owner’s manual. It will also include oil change instructions for your specific engine.

Check the manual or ask your Mercury authorised dealer for the recommended lubricant products for your marine engine.

Most four-stroke outboards and sterndrive engines require an oil change either annually or every 100 hours of operation.

Change engine oil before long-term or offseason storage, even if your seasonal use has not reached 100 hours. During operation, engine oil accumulates acidic combustion byproducts that can be harmful to internal engine components if left in the engine during storage.

Always replace the oil filter when you change the oil. There is no point in running clean oil through a dirty filter.

Warm the oil

Warm engine oil drains more quickly and completely than cold oil. When possible, plan to change your oil shortly after retrieving the boat from the water or run the motor on a flush hose for a few minutes before changing the oil (see your owner’s manual for flushing instructions).

Pump it

A Mercury oil drain pump (PN 802889A1) threads directly to the dipstick tube of many outboard, inboard and sterndrive engines and may be used to draw old oil from the sump, as an alternative to draining the oil. This method may allow you to complete an oil change with the boat in the water.

Use a filter wrench

A Mercury oil filter wrench can make it easier to remove and install the filter.

Check the gasket

Occasionally the oil filter O-ring gasket may stick to the engine after the oil filter is removed. Always carefully check the engine’s filter sealing surface for the old gasket. If you accidentally “double gasket” the new filter – screwing it on over the old gasket – it will likely leak and could cause engine damage.

Lubricate the gasket

Before installing a new filter, lubricate the rubber O-ring gasket on the filter with a finger dipped in clean engine oil. This allows the filter to seal against its mount without damaging or displacing the O-ring, which can also cause a leak.

Check your work

After completing the oil change, start the engine, either in the water or on a flush hose, and let it run for a few minutes. Then shut down and check the oil level on the dipstick. Also check for leaks around the oil filter. Starting the engine will circulate fresh oil through the engine before long-term storage.

Recycle

Always dispose of waste oil properly at an oil recycling facility.

Mercury oil filters

Designed to maintain a maximum oil flow rate and featuring high pleat counts for superior filtration levels, Mercury oil filters are the highest quality available for marine engine use. Mercury oil filters feature heavy duty canisters that will not leak, collapse or burst and an anti-corrosion coating that helps prevents the formation of rust or flaking that can block oil passages in the crankcase.

Oil change in a box

If you take pride in working on your own engine, a Mercury oil change kit is a convenient way to gather all the products you will need to do the job right. Available for many Mercury outboard models and for MerCruiser® sterndrive and inboard engines, each kit contains the appropriate quantity of Mercury 4-stroke marine engine oil along with a premium Mercury oil filter, a new drain-plug gasket and instructions.

Other lubrications points

Marine engines and drives have other lubrication points that may require an occasional service. See your Mercury Marine operation and maintenance manual for instructions specific to your engine.

Gearcase lubricant

Gearcase lubricant in outboard and sterndrive lower units should also be changed annually or at the service interval specified in the owner’s manual (typically after 100 or 200 hours of operation, depending on the model). Replacing the lubricant removes diminished additives and contaminants and provides an opportunity to inspect the lubricant for water.

Marine grease

Every Mercury outboard and MerCruiser sterndrive has a number of points that require application of grease as part of regular maintenance. Grease acts as both a lubricant between moving parts and as a moisture barrier to keep water out of those moving parts. You will need to apply grease with a finger and with a grease gun.

Power steering

Mercury Marine recommends lubricating the steering linkage and checking the power steering fluid level in Mercury Verado® outboards and MerCruiser sterndrives annually or every 100 hours.

Power trim fluid

The power trim and tilt fluid level should be checked annually or every 100 hours. It is common for the system to need a little fluid from time to time, but if it consistently needs fluid or if there are visible signs of a leak, contact a Mercury authorised dealer to get it checked out.

Mercury Precision Lubricants

Mercury 4-stroke marine engine oil

Mercury 4-stroke marine engine oil features a blend of high-quality base stocks and additives formulated specifically for use in most four-stroke outboard, sterndrive and inboard engines.

Mercury offers four-stroke engine oil in multiple grades and formulas to allow boaters to choose the ideal level of protection for their marine engine. As you move up the Good, Better, Best scale, engines benefit from higher refinement, superior additives and improved performance.

Mercury mineral-based 4-stroke marine engine oil

Mineral four-stroke oil is approved for use in all marine engines at the specified viscosity rating. This oil offers outstanding value paired with premium protection and is a good choice for use in low-horsepower outboards and engines that are not frequently operated under extreme performance applications or highly abusive conditions.  

Mercury synthetic blend 4-stroke marine engine oil

A balanced combination of the highest-quality synthetic and mineral base stocks offers outstanding engine and corrosion protection under high-torque/ high-rpm duty conditions, including in supercharged Mercury Verado outboards. Mercury synthetic blend oils deliver better performance than mineral-base oils in engines that are used frequently, in high-horsepower engines and in extreme temperature ranges.

Mercury fully synthetic 4-stroke marine engine oil

A fully synthetic oil is the ideal choice for avid boaters who want the highest level of protection against corrosion and wear. These highly refined oils are formulated to resist thermal breakdown in high-performance engines that are operated at or near maximum output and at high temperatures for extended periods of time, which is why they are a popular choice among tournament anglers and performance boat owners.

Mercury 2-stroke marine engine oil

Mercury 2-stroke marine engine oils exceed the NMMA TC-W3® standard and meet manufacturers’ recommendations for all two-stroke outboard and personal watercraft engines, in pre-mix or oil-injected applications.

Mercury Premium 2-stroke

Outboard oil is formulated to meet the needs of low to mid-horsepower outboard engines under general marine operating conditions. 

Mercury 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.

Mercury DFI 2-stroke

Oil is a synthetic-blend oil specifically formulated to meet the needs of Mercury OptiMax® and other direct fuel-injected (DFI) two-stroke outboard engines.

Mercury gear lubricants

There is no industry-wide standard for marine gear oils, so it is essential to use products specifically tested for marine applications. Mercury gear lubes contain a specialised marine additive package that outperforms automotive gear oil in marine gearcase applications.

Mercury Premium 80W-90 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 up to and including 75hp.

Mercury high-performance 90-weight gear lube

Provides maximum protection for sterndrive and outboard lower units above 75hp.  

Mercury racing extreme performance 85W-90 gear lube

This is recommended for use in high‑performance gearcases used in marine, power sports and motorsports applications. 

Mercury 2-4-C marine grease

Mercury 2-4-C marine grease is a versatile lithium-based grease that will not break down when exposed to water. It offers excellent resistance to oxidation and degradation and features extreme pressure additives to withstand friction in a wide variety of applications and range of temperatures. Ideal for use as a general-purpose marine grease.

Next topics

Maintenance: What's in it for you?

Boating is an activity that fuels pride of ownership, and for many owners a strong do-it-yourself attitude. Knowing you have covered the basics of maintenance gives you confidence that your boat is in tip-top shape every time you leave the dock.

Fuel basics

Using the correct fuel in your Mercury Marine® engine and properly maintaining your fuel system can help ensure many seasons of reliable service. For more guidance on fuel requirements for your engine, see the fuel section of your Mercury® operation and maintenance manual.

Preventing corrosion

Your engine lives and works in the water, where it is constantly exposed to elements that can cause corrosion.