Mercury – 25W-40 4-Stroke Marine Engine Oil, 1 Quart | FourStroke Lubrication Series | Marine Engine Oil | 8M0078627

Overview

Marine engines live a harder life than most people realize. One day it’s a long, hot run across open water, the next it’s slow idling in a tight channel with humid air hanging over the stern. That mix of heat, moisture, and load is exactly why the right oil matters. When you’re using a true marine oil, you can feel the difference in how steady the engine sounds and how confident it feels when you lean into the throttle.

This Mercury Marine part is the quart bottle I reach for when I want simple, reliable protection without guessing. It’s built for four-stroke outboards, sterndrives, and inboards that call for 25W-40. Pour it in, follow your service schedule, and enjoy that quiet peace of mind that comes from doing the basics right.

Key Features

• Four-stroke marine engine oil formulated for harsh, corrosive boating environments
• Viscosity rating: 25W-40
• Designed to provide outstanding wear protection and corrosion resistance
• Industry-focused strength and viscosity retention for consistent protection under load
• Certified to meet FC-W standards and catalyst compatible FC-W standards
• Recommended for Mercury, MerCruiser, and many other four-stroke marine engines where 25W-40 is specified
• Produced by Mercury Marine to original equipment manufacturer specifications
• Bottle size: 1 quart
• Mercury Marine part number 8M0078627

Engine & Boat Compatibility

• Four-stroke outboard engines that specify 25W-40 marine oil
• Four-stroke sterndrive engines that specify 25W-40 marine oil
• Four-stroke inboard engines that specify 25W-40 marine oil
• Common on bass boats, pontoons, center consoles, cruisers, and family runabouts
• Always confirm oil grade and capacity in your owner’s manual

Performance & Practical Benefits

A good oil change doesn’t just protect the engine, it changes how the day feels. With the right 25W-40 marine oil, your engine tends to run smoother when it’s warm, stay more consistent under steady cruise, and feel less strained when you’re pushing into chop. This is the kind of oil designed to hold its viscosity when the engine is working hard, which matters when you’re running higher revolutions per minute for long stretches.

The corrosion protection is a big part of the story, too. Boats sit. They cool down. Moisture sticks around. That’s when corrosion likes to start quietly doing damage. A marine-focused additive package helps protect internal parts both on the water and during downtime, which is exactly what weekend boaters need.

It’s also practical for maintenance. The quart size is easy to handle, easy to store onboard or in the garage, and simple to measure. Whether you’re topping off or doing a full service, it keeps the process clean and straightforward.

Why Buy OEM

Oil is one of those things that’s easy to overcomplicate, but it doesn’t have to be. Using a genuine Mercury Marine part means you’re choosing a formula built specifically for marine engines, not something borrowed from the automotive world. It meets recognized marine standards, supports warranty-minded requirements, and is designed to protect the engine the way Mercury intended.

Aftermarket oils can work, but not all are truly marine-certified or focused on corrosion the same way. If you want an easy, reliable choice that performs right the first time and stays consistent over the season, OEM is the practical move.

FAQ Section

Q1: Which Mercury engines or systems does the 25W-40 4-Stroke Marine Engine Oil fit?

It’s intended for four-stroke outboard, sterndrive, and inboard engines where 25W-40 marine oil is recommended in the owner’s manual.

Q2: What makes this part different from aftermarket alternatives?

It’s produced by Mercury Marine to original equipment manufacturer specifications and certified to meet FC-W and catalyst compatible FC-W marine standards.

Q3: How do I know if this is the correct replacement for my setup?

Check your owner’s manual for the required viscosity and marine certification, then match the part number to 8M0078627.

Q4: Can this be used in both saltwater and freshwater applications?

Yes. It’s designed for marine use in general, including saltwater conditions where corrosion protection is especially important.

Q5: Is installation straightforward for most boat owners?

Yes. Most owners can handle an oil change with basic tools and the correct procedure. If you’re unsure, a marine shop can service it quickly.