Motor Oil Info

Viscosity is the most important property of a lubricant in it defense against friction and wear. Viscosity correlates to film thickness and film strength, which keep moving parts from contacting each other and creating increased friction, heat and wear. The higher the viscosity of a lubricant, the greater protection it provides. Note, however, that too thick a lubricant is detrimental because it consumes more energy.

Many gear lubes are formulated with additives called viscosity index improvers (VI). These additives broaden a lubricant’s operating temperature range and are used to ensure multigrade viscosity performance for hot and cold temperatures. VI improvers keep lubricants from becoming too thick to flow in cold temperatures and too thin to protect in high temperatures. However, shearing forces within equipment can cause these additives to break down and lose viscosity.

AMSOIL Severe Gear, Synthetic Gear Lubes demonstrate superior viscosity index and shear stability properties, and they are better-equipped to protect equipment against the devastating effects of thermal runaway. Severe Gear Synthetic Gear Lubes are blended with superior high (VI) viscosity improvers, shear stable synthetic base oils and an overtreatment of extreme pressure additives that effectively protect high-stress applications against friction, heat and wear.

Keeping equipment in top working order and ensure summer trips aren’t ruined by a broken-down vehicle. Specifically engineered for high-demand applications, including trailer towing, heavy hauling, 4×4 off-road driving, commercial use and racing.

Viscosity is the most important property of a lubricant in its defense against thermal runaway. Viscosity correlates to film thickness and film strength, which keep moving parts from contacting each other and creating increased friction, heat and wear. The higher the viscosity of a lubricant, the greater protection it provides. However, a lubricant which is too thick is detrimental because it consumes more energy and increases fuel consumption.

The original equipment manufacturer (OEM) determines which viscosity grade is optimum for the specific application. Many gear lubes are formulated with additives called viscosity index (VI) improvers. These additives broaden a lubricant’s operating temperature range and are used to ensure multi-grade viscosity performance for hot and cold temperatures.

The extreme pressures and temperatures generated by modern vehicles increase stress on gear lubricants and can lead to a serious condition known as thermal runaway. As temperatures in the differential climb upward, gear lubricants lose viscosity and load carrying capacity. When extreme loads break the lubricant film, metal-to-metal contact occurs, increasing friction and heat. This increased friction and heat, in turn, results in further viscosity loss, which further increases friction and heat.

As heat continues to spiral upward, viscosity continues to spiral downward. Thermal runaway is a vicious cycle that leads to irreparable equipment damage from extreme wear, and ultimately catastrophic gear and bearing failure.

Another summer season is underway, and with summer comes a wide variety of recreational activities such as fishing, boating, jet skiing and ATV and dirt bike riding. Many enthusiasts use trailers to tow their equipment, and in order to avoid any inconvenient and expensive breakdowns, it is crucial to ensure proper maintenance has been performed on the tow vehicle’s drivetrain. Nothing will ruin a weekend quicker than becoming stranded on the side of the road.

Severe duty activities such as towing heavy trailers, hauling heavy loads and off-roading place an increased level of stress on drivetrain components. Modern vehicles such as turbo diesel trucks and vehicles with V-10 engines boast more horsepower and torque than their predecessors, but differential designs have remained virtually unchanged through the years. Differentials today are subjected to severe duty service and encounter more stress and heat than was seen only a few years ago. So a gear lube fluid change is a great idea.

Some manufacturers recommend changing the factory-fill gear lube within the first 500 to 3,000 miles based on SAE test stand and field tests. AMSOIL recommends the factory-fill differential gear lube be changed no later than the first 5,000 miles, even when vehicle manufacturers do not specify to change the factory-fill gear lube to remove wear particles.

When using AMSOIL synthetic gear lubes, AMSOIL recommends drain intervals of 50,000 miles in severe service or 100, 000 miles in normal service, or longer if stated by the OEM. AMSOIL synthetic gear lubes not only offer second-to-none protection and performance in cars and light trucks, including turbo diesel pickup trucks, they are much less expensive than OEM synthetic gear lubes. Changing break-in wear particles out after the first 5,000 miles of service and using AMSOIL synthetic gear lubes at the correct recommended gear lube drain interval ensures long, trouble-free differential life.

According to a 2005 SAE paper entitled Breaking the Viscosity Paradigm: Formulating Approaches for Optimizing Efficiency and Vehicle Life, ” Concurrent with the strong drive toward better fuel economy, consumers have been demanding increased performance, which has required axle lubricants with enhanced durability protection and lower operating temperatures. There has been a 34% increase in engine horsepower over the last decade, while axle gear sizes have remained constant, sump capacities have been lowered, and drain intervals extended. In the light truck segment there has been a 93% horsepower increase since 1981.”

Most differential wear occurs during the break-in period. Because differentials are not equipped with filters, break-in metals are suspended in the oil, causing increased wear as the particles mesh between the gears. Hauling heavy loads and towing trailers cause additional stress to the differential during the break-in period and can cause premature differential damage. Changing the gear lube after the break-in period (about 5,000 miles) greatly reduces wear and extends differential gear and bearing life. Auto manufacturers are beginning to recognize the importance of drain abrasive break-in materials. Some manufacturers recommend an interval of between 500 and 3,000 miles. The best way to go, is to replace your gear lube with Synthetic Gear Lube.

Further evidence of stress and increased temperatures during the differential break-in period is documented in a 2005 SAE paper entitled The Effect of Heavy Loads on Light Duty Vehicle Axle Operating Temperature. A light duty GM truck towing 14,000 pounds was driven from Orange County, Calif. to the Nevada state line. The test was conducted with both a new axle and a broken-in axle. Over level ground towing, oil temperature was measured at 110 degrees F in the new axle and 95 degrees F in the broken-in axle. Oil temperature over the most grueling portion of the trip, during which a maximum 6% grade was encountered, revealed the new axle was operating at 350 degrees F and the broken-in axle was operating at 300 degrees F. Laboratory dynamometer test results simulating a truck hauling a trailer provided similar results, with level ground towing temperatures recorded at 266 degrees F with the new axle and 194 degrees F with the broken-in axle and towing temperatures (at a 3.5% grade) recorded at 370 degrees F with the new axle and 295 degrees F with the broken-in axle.

AMSOIL Severe Gear 75w-90 and 75w-140 Synthetic Gear Lubes are formulated for severe service applications, protecting differential gears for extended drain intervals of up to 50,000 miles in severe service and 100,000 miles in normal service, or longer where specified by the vehicle manufacturer. Formulated with shear stable synthetic base stocks and an extra treatment of additives, Severe Gear, Gear Lubes provide unsurpassed wear protection and friction reduction, while their excellent thermal stability prevents thermal runaway, a phenomenon caused by lubricant’s inability to control friction and increased heat under high stress conditions.