AMSOIL SEVERE GEAR® 80W-90 100% SYNTHETIC GEAR LUBE

AMSOIL SEVERE GEAR 80W-90 100% Synthetic Gear Lube delivers heavy-duty wear protection and thermal stability for differentials, manual transmissions, and transfer cases operating under punishing conditions. It is built for trucks, SUVs, heavy equipment, and any vehicle where towing, hauling, steep grades, or high ambient temperatures push conventional gear oil past its limits.

Modern pickups and SUVs generate more horsepower and towing capacity than ever before. That puts enormous stress on ring-and-pinion gears, bearings, and synchronizers, especially in rear differentials under load. Conventional 80W-90 gear oils can lose viscosity as temperatures climb, thinning out right when protection matters most. The result is accelerated wear, increased noise, and shortened component life.

CONTROLS THERMAL RUNAWAY
Thermal runaway happens when a gear lubricant can no longer control friction-generated heat. As the oil thins, friction increases, which generates more heat, which thins the oil further. It is a destructive cycle that can damage gears and bearings rapidly. AMSOIL SEVERE GEAR 80W-90 is formulated to resist viscosity loss under extreme thermal stress, breaking the cycle before it starts. It resists breakdown from high heat and prevents acid and carbon/varnish formation that degrade both the lubricant and the components it protects.

IRON-SULFIDE BARRIER COATING FOR WEAR PROTECTION
Under high-load conditions, gear teeth experience extreme pressure at their contact points. AMSOIL SEVERE GEAR uses proprietary additives that form an iron-sulfide barrier coating directly on gear surfaces. This coating acts as a sacrificial wear barrier, protecting against pitting, scoring, and metal-to-metal contact even when fluid film thickness is marginal. For trucks like a Ram 2500 towing a fifth wheel or a Ford F-250 pulling a gooseneck trailer, this level of extreme-pressure protection is critical for long differential life.

EXCELS IN TEMPERATURE EXTREMES
SEVERE GEAR 80W-90 is a fully synthetic, wax-free formulation. That matters at both ends of the thermometer. In cold weather, wax-free construction provides better cold-flow properties compared to conventional mineral-based 80W-90 gear oils, improving cold-weather shifting in manual transmissions and reducing drag in differentials during startup. The Brookfield viscosity measures 23,200 cP at -23°C (ASTM D2983), confirming its cold-temperature fluidity. In hot conditions, a flash point of 206°C (403°F) per ASTM D92 and a viscosity index of 132 (ASTM D2270) demonstrate its ability to maintain a protective lubricant film at elevated operating temperatures. This combination helps reduce operating temperatures by lowering internal friction.

COMPATIBLE WITH LIMITED-SLIP DIFFERENTIALS
SEVERE GEAR 80W-90 contains friction modifiers for most limited-slip differential applications. Vehicles like the Chevrolet Silverado, GMC Sierra, Toyota Tacoma, and Jeep Wrangler with factory limited-slip differentials can use this product directly. For applications that require additional limited-slip friction modifier, AMSOIL Slip Lock can be added.

LONG SERVICE LIFE
Extended drain intervals reduce maintenance costs and downtime. In cars, SUVs, and light trucks under normal service, SEVERE GEAR 80W-90 is good for up to 100,000 miles (161,000 kilometers) or per the owner's manual, whichever is longer. Under severe service conditions such as towing, hauling, frequent stop-and-go, or high ambient temperatures, the interval is 50,000 miles (80,500 kilometers) or per the owner's manual, whichever is longer. For heavy-duty Class 8 line-haul trucks, the OEM drain interval for synthetic oil applies up to 250,000 miles (402,500 kilometers) or three years. Vocational and delivery vehicles are covered up to 120,000 miles (193,200 kilometers) or three years. Heavy-duty off-road equipment is supported up to 100,000 miles or two years.

Gear oils should be changed more frequently when operating in dusty or dirty conditions, unless the gear system is properly sealed and equipped with membrane-type breathers. AMSOIL does not support extended drain intervals where water contamination occurs.

SPECIFICATIONS AND COMPATIBILITY
AMSOIL SEVERE GEAR 80W-90 meets API GL-5, MT-1, MIL-PRF-2105E, Dana SHAES 234 (formerly Eaton PS-037), and Mack GO-J. It also satisfies other GL-5-based specifications from Ford, GM, and Chrysler, and can be used in axles where an API GL-4 lubricant is recommended. It is compatible with conventional and synthetic gear oils, though mixing will shorten oil life expectancy and reduce performance benefits. AMSOIL does not support extended drain intervals where oils have been mixed. Aftermarket oil additives other than those specified by AMSOIL are not recommended.