Mercury – SAE 25W-40 Synthetic 4-Stroke Marine Oil, 1 Gallon | Lubrication | 92-8M0078630

Overview

Four-stroke marine engines don’t get an easy break. They idle for long stretches, jump straight into hard throttle, and spend their whole life in heat and humidity. That’s why the oil you pick matters. This 25W-40 synthetic blend is the kind of oil most mechanics stick with because it hangs onto its thickness, keeps metal parts coated on cold starts, and does a solid job fighting the corrosion that sneaks into every marine engine. If you want your motor to stay strong season after season, this is the kind of oil you run.

Key Features

 • For Any 4-Stroke Marine Engine – Outboards, sterndrives, inboards—they all run well on it.
 • Synthetic Marine Formula – Built to handle salt, heat, and long run times.
 • Holds Viscosity Under Load – Doesn’t thin out when things get hot.
 • 25W-40 Weight – A favorite viscosity for many Mercury four-strokes.
 • 1-Gallon Jug – Enough to handle a full oil change on most mid-size engines.

Engine & Boat Compatibility

 • 4-stroke outboards
 • MerCruiser sterndrives
 • Inboard 4-stroke engines
 • FC-W and FC-W catalyst-rated systems

Performance & Practical Benefits

Most motors feel noticeably smoother once they’re running on fresh 25W-40. Idle settles down, cold starts don’t sound as harsh, and the engine feels a bit more confident when you push the throttle forward. The oil holds up well over long days, so you don’t get that thin, noisy feel older oil can cause. It also keeps varnish and sludge from building up, which makes life easier when you’re maintaining the engine down the road.

Why Buy OEM

Mercury blends this oil for the exact kind of punishment marine engines deal with—heat under the cowling, moisture in the air, long idle cycles, and quick bursts to high RPM. Automotive oils simply aren’t built for that. With OEM oil, you know you’re giving the engine what it was designed to run on.

FAQ

Q1: How often should this oil be changed?
A: Most boaters change it once per season or at the recommended service hours, whichever comes first.

Q2: Is mixing this with other oils okay?
A: Better not. Keeping one formula in the engine gives you consistent protection.

Q3: Is it safe for saltwater boats?
A: Yes—its corrosion-fighting additives are meant for exactly that environment.

Q4: Will this help cold starts?
A: It usually does. The synthetic blend sticks to parts better, so starts aren’t as dry.

Q5: Why avoid automotive oil?
A: Car oil breaks down too fast in marine heat and humidity. Marine engines need something tougher.