Lucas Oil Synthetic SAE 75W-90 Marine Gear Oil — 1 Quart, Anti-Wear & Corrosion Protection

Lucas Oil M8 Synthetic SAE 75W-90 Marine Gear Oil is a full-synthetic, non-foaming marine gear lubricant engineered to reduce wear and corrosion in outboard and sterndrive gearcases.

This 1-quart formulation was developed from racing-proven chemistry to meet the demands of high-performance offshore boats while remaining suitable for everyday marine use. The advanced synthetic base and tailored additive package help protect gears, bearings, and seals from the unique stresses of salt and fresh water environments, as well as long storage intervals between seasons. Lucas added seal conditioners and exclusive anti-wear and anti-corrosion components to maintain smooth shifting, minimize foam, and resist breakdown under heat and shear.

How does this oil protect marine gears during storage and seasonal layup?

Lucas M8 includes corrosion inhibitors and seal conditioners that cling to metal surfaces and elastomers, forming a protective film. That film helps prevent rust and hardening of seals when boats sit unused for extended periods.

• Long-lasting synthetic film resists oxidation and corrosion
• Seal conditioners keep elastomers pliable during storage
• Non-foaming formula reduces aeration that can promote corrosion

Will this lubricant perform under high load and high-power racing conditions?

Originally formulated for offshore racing, the SAE 75W-90 viscosity grade provides a balance of low-temperature flow and high-temperature film strength for extreme loading and high RPMs. The additive package reduces metal-to-metal wear even under heavy loads and shock conditions.

• Synthetic base resists shear and maintains viscosity under high stress
• Advanced anti-wear additives protect gear teeth and bearings
• Stable under heat for consistent lubrication during extended high-speed operation

Is this oil compatible with my boat’s seals, bearings, and existing gear oil?

Lucas M8 is formulated for marine gearcases and includes seal conditioners to help maintain elastomer health. Always check your equipment manufacturer’s specifications for required viscosity and approved product types before switching lubes.

• Contains seal conditioners to preserve common marine elastomers
• Suitable where SAE 75W-90 is specified by the manufacturer
• Refer to owner’s manual; mixing with unknown fluids is not recommended

How does it stand up to salt water exposure and corrosion risks?

The product’s corrosion inhibitors and synthetic base provide enhanced resistance to salt-water induced degradation compared with conventional oils. It is formulated to protect metal surfaces and reduce the chance of pitting and surface rust.

• Anti-corrosion chemistry protects exposed internal components
• Synthetic formulation resists water contamination effects better than mineral oils
• Helps maintain gearcase integrity during intermittent water intrusion events

Who this is for: Lucas Oil M8 Synthetic SAE 75W-90 Marine Gear Oil is aimed at owners and operators of performance and recreational boats with outboard, stern drive, or inboard gearcases that call for a 75W-90 marine gear lubricant. It's especially useful for mariners who need dependable protection through high-power use, frequent saltwater exposure, or long storage periods. As with any lubricant, follow the vehicle manufacturer’s recommendations in your owner’s manual for best fit and performance.

For best performance, follow the manufacturer's recommendations in your vehicle owner’s manual.