Royal Purple Max Gear 85W-140 Synthetic Gear Oil 1 qt — High-Pressure, Low-Friction Protection

Royal Purple Max Gear 85W-140 is a full-synthetic, high-performance gear oil engineered to protect heavily loaded differentials and manual transmissions while improving shift quality and reducing gear wear.

Developed with Royal Purple's Synerlec additive chemistry and premium synthetic base stocks, Max Gear 85W-140 is formulated to withstand extreme pressure, high heat and the shock loads typical of trucks, RVs, and heavy-duty automotive gearsets. This 1‑quart pack offers a concentrated, long-wearing lubricant that helps gears operate more quietly and resist the degradation that comes with heavy service. It meets API GL-5 and GL-4 specifications and contains hypoid friction modifiers suitable for clutch or cone-type differentials without needing extra additives.

How does this gear oil protect gears under heavy loads?

Max Gear uses a combination of synthetic base oils and a proprietary additive pack to form a tough protective film on gear surfaces. That film reduces metal-to-metal contact during high torque or shock loading, cutting wear and extending component life.

• Synerlec additive package for enhanced film strength and wear resistance
• High-pressure performance for hypoid gears and heavy-duty differentials
• Low friction formulation to reduce heat and improve efficiency
• Compatible with GL-5 and GL-4 systems—no extra additives required

Will this oil work in my vehicle's differential or manual transmission?

Max Gear 85W-140 is recommended for automotive and truck front or rear differentials, manual transmissions, and lower units of marine engines that call for GL-5 or GL-4 fluids. Always check your owner’s manual for the manufacturer’s specified viscosity and API rating before use.

• Meets API GL-5 and GL-4 performance levels
• Hypoid friction modifiers included for clutch/cone differentials
• Suitable for heavy-duty truck, RV, and automotive gear applications
• Compatible with conventional oils for top-up or changeovers

How does this oil perform across temperature extremes?

The synthetic base oils in Max Gear maintain stable viscosity at elevated temperatures while retaining adequate flow at lower temperatures for reliable gear engagement. That thermal stability helps reduce thermal breakdown, improves water separation and keeps lubricating films intact during prolonged heat exposure.

• High-temperature stability for sustained protection under load
• Good low-temperature fluidity for faster gear lubrication on cold starts
• Effective water separation to limit corrosion and lubricant degradation

What are the concrete benefits I’ll notice after changing to this oil?

After switching to Royal Purple Max Gear 85W-140 you can expect smoother gear meshes, quieter differentials under load, and reduced wear rates compared with many conventional gear oils. Improved thermal resistance and film strength help extend drain intervals when used according to vehicle recommendations.

• Smoother shifting and reduced gear noise in heavy-duty use
• Lower coefficient of friction for improved mechanical efficiency
• Enhanced wear protection for longer gear life and fewer repairs
• No additional additives necessary—ready to use out of the bottle

Who is this for? Royal Purple Max Gear 85W-140 is intended for owners and technicians of trucks, motor homes/RVs, performance vehicles, and marine lower units that require an API GL-5 or GL-4 gear oil. It's especially suited to vehicles and equipment subjected to high torque, towing, or sustained heavy loads where stronger films, better thermal stability and quieter operation are priorities. Always follow your vehicle manufacturer’s viscosity and specification guidelines when choosing and installing gear oil.

Manufacturer notes:

• Follow the vehicle owner’s manual for best performance and correct application.
• Compatible with other oils, though mixing may alter performance characteristics.
• No additional additives are required—the product is fully formulated.