STAR BRITE Synthetic Blend 80W-90 Lower Unit Gear Lube — Marine Grade, GL-5/MT-1 Protection for 100+ HP

STAR BRITE Synthetic Blend 80W-90 Lower Unit Gear Lube is a marine-grade gear oil formulated to protect outboard lower units from wear, rust, and thermal stress while delivering reliable lubrication for engines over 100 hp.

Whether you're routine-maintaining a weekend boat or preparing a long cruise, the right lower unit lubricant matters. This 80W-90 synthetic blend meets API GL-5, MT-1, SAE J2360 and Mack GO-J specifications and combines extreme-pressure and anti-wear additives for stable performance under load and heat. It’s designed as an upgrade for common marine gear lube applications and pairs with STAR BRITE's line of pumps, tubes, and adapters to simplify service.

How does this gear lube protect my lower unit under heavy use?

The formula includes extreme-pressure and anti-wear additives that maintain film strength at elevated temperatures and protect gear surfaces during hard loads. Its high viscosity helps retain a protective oil layer between metal parts, resisting metal-on-metal contact and reducing micro-pitting.

• Extreme-pressure agents reduce scoring and surface fatigue.
• Anti-wear chemistry lowers friction and extends gear life.
• High-viscosity base provides consistent lubrication at speed.

Will this oil work with my engine and gear specifications?

This 80W-90 blend is suitable for most outboard lower units requiring GL-5/MT-1 grade oils and is recommended for engines above 100 hp. It complies with SAE J2360 and Mack GO-J standards, making it compatible with a wide range of marine gearboxes and drives.

• Meets API GL-5 and MT-1 service classifications.
• Engineers to SAE J2360 and Mack GO-J specifications.
• Recommended for high-horsepower outboards and many lower unit designs.

How simple is it to change the lower unit oil with STAR BRITE products?

Draining and refilling is straightforward when you follow the guide: remove drain plugs, allow old oil to flow out, install the fill tube, pump in fresh lube, and reseal plugs. STAR BRITE sells quart pumps, lube tubes, and adapters to make the refill clean and quick.

• Step-by-step flushing and filling guidance included.
• Compatible accessories (pumps, tubes, adaptors) sold separately.
• Minimizes spills and speeds service intervals on the water.

What performance benefits can I expect from switching to this synthetic blend?

Switching to a synthetic blend delivers improved thermal stability, better wear protection, and extended resistance to rust and corrosion compared with many conventional gear oils. The formulation helps maintain consistent viscosity across operating temperatures, which aids smooth shifting and quieter operation.

• Better thermal stability reduces viscosity breakdown in heat.
• Corrosion inhibitors protect exposed metal during storage and use.
• Improved anti-wear performance lowers maintenance frequency.

Who is this for: Boaters and marine technicians who operate or maintain outboards and sterndrives—especially engines over 100 hp—will benefit from this marine-grade 80W-90 gear lube. It suits owners seeking a dependable, specification-compliant lubricant that pairs with STAR BRITE service tools for cleaner, faster lower-unit maintenance. Choose this product if you want broad compatibility, enhanced wear protection, and equipment-preserving performance from a trusted U.S.-based marine brand.