Viscosity Protection
Hard working diesel engines present a serious challenge to the lubricants that protect them. Tight clearances and intense pressures can generate enough force to tear apart the molecular structure of the oil, causing permanent viscosity loss. Permanent viscosity loss is termed “shear” and leads to accelerated equipment wear, oil consumption and deposit formation.
Shear stability measures lubricant’s ability to withstand shearing forces without degrading to a lower viscosity. To meet CJ-4 requirements for shear stability, the American Petroleum Institute (API) requires diesel oils to pass the Kurt Orbahn 90-Cycle Shear Stability Test.
Resisting shear and maintaining protective viscosity in the harsh operating conditions of diesel engines is challenge enough for many diesel oils, but maintaining viscosity in the face of fuel dilution is another challenge altogether. Factors such as frequent starts, excessive engine idling short trips and cold weather have contributed to moderate levels of fuel dilution in diesel applications for years, while recent issues with emission systems have brought the fuel dilution problem to a whole new level.
