Mercury – 80W-90 Premium Gear Lube | Outboards and Sterndrives | Marine Formula | 858059K01

Overview

There is a kind of comfort that only comes from knowing your gear can take a beating and still perform like new. Mercury 80W-90 Premium Gear Lube delivers exactly that — protection you can trust, mile after mile on the water. It is designed for boaters who don’t baby their engines, who run hard, who push through waves without hesitation. This oil doesn’t just lubricate; it gives your lower unit the confidence to keep going strong when conditions get rough.

Key Features

• Formulated to prevent corrosion and wear under marine stress
• Built for outboard engines below 75 horsepower
• Features improved emulsifiers for protection if water enters the gear housing
• 80W-90 viscosity ensures steady performance in variable conditions
• Comes in a 2.5-gallon jug for convenient, long-term maintenance
• Meets Mercury Marine OEM engineering standards

Engine & Boat Compatibility

• Ideal for Mercury and Mariner outboards under 75 HP
• Compatible with lower gear housings and small sterndrive units
• Perfect for fishing boats, pontoons, and small runabouts
• Suitable for use in saltwater and freshwater environments

Performance & Practical Benefits

When you rely on your boat week after week, your lower unit oil needs to do more than meet specs — it needs to hold up under real-world stress. This Mercury Marine part was designed for exactly that. It maintains a tight film of protection that keeps metal from grinding and water from corroding your gears. The result is smoother shifts, stronger torque transfer, and quieter performance, even after long hours on the throttle.

You’ll notice how clean it feels — less chatter, more control, and a lower chance of internal damage when conditions get unpredictable. And because it resists breakdown under heat, you get lasting protection no matter how long you run. The 2.5-gallon size makes it perfect for seasoned boaters who take maintenance seriously and prefer to stock up on quality.

Why Buy OEM

When it comes to your lower unit, shortcuts aren’t worth it. This genuine Mercury OEM oil was tested and approved by the same engineers who designed your outboard. That means it fits your system perfectly — no guessing, no compromise. Aftermarket gear oils can’t replicate the marine-grade corrosion resistance and anti-foaming stability Mercury builds into every batch.

It’s more than just oil — it’s the peace of mind that comes from knowing your gearcase is protected by the people who built it.

FAQ Section

Q1: Which engines use Mercury 80W-90 Gear Lube 858059K01?

It’s for Mercury and Mariner outboards up to 75 horsepower, and compatible lower units.

Q2: What’s different about it?

Its advanced emulsifiers keep gears safe even if water enters the case.

Q3: How do I know it fits my setup?

If your manual lists part number 858059K01, this is the correct OEM fluid.

Q4: Is it for saltwater?

Yes, it’s designed for both environments with strong corrosion inhibitors.

Q5: Is it easy to store and use?

Yes — the 2.5-gallon jug is ideal for garages or onboard spares.