As the testing indicates, AMSOIL Severe Gear ranked highest among all gear lubes tested. It was the only gear lube to score a 4 or better in all performance categories. The high ranking of AMSOIL Severe Gear clearly points to a well-balanced formulation capable of delivering effective, long-lasting lubrication protection to all differential components. Most notable is the superior performance of AMSOIL Severe Gear in the critical areas of extreme-pressure protection and viscosity and oxidation stability. Based on the performance testing, the slightly higher than average price of AMSOIL Severe Gear would be offset by the cost savings achieved through reduced maintenance, longer lasting differentials and extended lubricant life.

Some gear lubes tested well in some areas but scored low marks in others. Torco SGO Synthetic scored highest in viscosity index and cold-temperature Brookfield viscosity but sheared out of grade, failing the SAE J306 requirements for SAE 75W-90 gear lubes. Mopar and Royal Purple scored well in the 4-Ball EP Weld Test, but failed the Copper Corrosion Test and GM, with a good 4-ball EP score, foamed badly after oxidation. This would indicate that too much emphasis in one area of formulation can detract from performance in others. A gear lube is only as good as its weakest link.

A well-balanced gear lube formulation, therefore, is critical for differentials in all types of vehicles, both standard and  high-performance.

With more horsepower, more towing capacity, higher hauling limits and changes in vehicle design, more stress than ever is placed on differential gears. High-quality lubrication is essential, and awareness is now necessary to ensure maximum differential performance and to avoid costly repairs. When purchasing gear lube the decision is left to the consumer, yet based on the facts reported in this document, AMSOIL Severe Gear is the logical choice.

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