ABSTRACT
The objective of crankcase oil is to lubricate various hardware surfaces in order to minimize metal-to-metal contact and to reduce friction and wear. In general, crankcase oils perform a number of important functions all designed to protect and prolong the overall life of the engine. Prior to 1988, North American heavy-duty diesel engine oils were formulated to control three major performance parameters: upper piston deposits, engine wear, and engine corrosion. In 1994, particulate emissions become even tighter leading to increased soot levels in engine oils. In crankcase lubricants formulations, the base oil is composed of a single base stock or a blend of several base stocks. Lubricants exhibit an inverse viscosity-temperature relationship, their kinematic viscosity decreases with the increase in temperature. Crankcase lubricants viscosity grades are defined in the SAE J300 Engine Oil Viscosity Classification. This document describes the viscosity profiles of lubricants formulated to protect 4–stroke/2 stroke engines.
