Mercury – 25W-40 4-Stroke Marine Engine Oil, 1 Quart | FourStroke Lubrication Series | 25W-40 Marine Oil | 8M0078619

Overview

There’s a certain comfort in hearing your engine settle into a smooth idle after you launch. No rattles, no hesitation—just that steady, familiar hum that tells you everything is ready. Clean oil is a big part of that feeling, especially on a boat where heat, humidity, and salty air are always trying to wear things down. When you’re counting on your motor to bring you back after a long run, you don’t want to wonder if your oil can keep up.

This Mercury Marine part is a straightforward, dependable 25W-40 oil made for real marine use. It’s the kind of quart you keep on hand for a proper service or a mid-season top-off, so your engine keeps running smooth and confident all year.

Key Features

• Four-stroke marine engine oil designed for sterndrive and outboard applications
• Viscosity rating: 25W-40
• Formulated for superior corrosion resistance and wear protection
• Built to help reduce friction and protect internal components for long engine life
• Special viscosity modifiers help support performance of high-revolutions-per-minute four-stroke outboards
• Meets or exceeds marine industry requirements, including FC-W and catalyst compatible FC-W standards
• Bottle size: 32 fluid ounces (1 quart)
• Mercury Marine part number 8M0078619

Engine & Boat Compatibility

• Designed for use in four-stroke marine engines
• Suitable for many four-stroke outboards that specify 25W-40
• Suitable for many four-stroke sterndrive applications that specify 25W-40
• Common on bass boats, pontoons, center consoles, bay boats, family runabouts, and cruisers

Performance & Practical Benefits

Marine engines ask a lot from oil. One trip might be a long cruise at speed, the next might be idling through no-wake zones with the sun baking the cowling. Oil has to protect across that whole range. This 25W-40 is built to hold up under heat and maintain its protective film so the engine stays feeling tight and steady when you’re running hard.

Corrosion protection is where marine oil really proves itself. Boats sit between trips, often in damp air, and that downtime is when moisture can do damage quietly. A corrosion-resistant formula helps protect internal parts even when the engine isn’t running, which is exactly what weekend boaters need. Over time, that can mean fewer issues that creep up slowly—sticky components, extra wear, or performance that just doesn’t feel as crisp.

The quart size keeps things practical. It’s easy to pour, easy to store, and perfect for topping off after service or keeping in the garage for the next oil change. When your routine is simple, you’re more likely to stay on schedule, and your engine benefits every time.

Why Buy OEM

Oil isn’t the place to guess. A genuine Mercury Marine part like this is made to meet marine standards and protect against the specific threats engines face on the water—corrosion, heat, and sustained load. It’s designed for fit-for-purpose marine performance, not automotive shortcuts.

Aftermarket oils vary widely, and some don’t offer the same marine-focused corrosion resistance or certified performance. OEM keeps it straightforward: the right viscosity, the right protection, and reliable results that support long-term engine health.

FAQ Section

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

It’s designed for four-stroke marine engines, including many outboards and sterndrives that specify 25W-40 in the owner’s manual.

Q2: What makes this part different from aftermarket alternatives?

It’s built to meet marine industry requirements, including FC-W and catalyst compatible standards, with corrosion resistance designed for boating conditions.

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

Check your owner’s manual for the recommended viscosity. If it calls for 25W-40, match the part number to 8M0078619.

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

Yes. It’s formulated for marine use in either environment, with corrosion protection that’s especially helpful in saltwater.

Q5: Is installation straightforward for most boat owners?

Yes. Use it for standard oil changes or top-offs. Follow your manual for capacity, change intervals, and proper disposal.