Fighting Mechanical Shear in Diesel Engine Oil

Lubricant shear stability has been defined as “the property of an oil to resist the action of shear forces and the related mechanical destruction by breaking and tearing. It is the resistance to changes in viscosity.” [1]

As noted by Savant Labs, “most multigrade lubricants are formulated with viscosity modifiers in order to increase the viscosity index (VI) to ensure the lubricant can provide a sufficient film thickness to protect the equipment or engine from wear. Viscosity modifiers (VM) tend to be polymer-based chemistry that are susceptible to shear thinning. When a lubricant undergoes shear thinning, the viscosity of the fluid can be lowered by an entire ISO grade leaving moving parts in danger of wear or seizure. ”[2]