For the past 50 years the specification and testing of lubricant performance has successfully protected engines and powertrains against wear, internal deposit formation, and corrosion while reducing friction. Lubricant systems have systematically evolved in concert with increased performance requirements arising from

• Higher engine operating temperatures from increased power densities and reduced aerodynamic cooling;

• Extended service drain periods in response to consumer expectation and market expansion;

• Improvements and changes in fuel quality, mainly for reductions in sulfur but also gradual reformulations, then inclusion of biofuels at (currently) low percentages; and

• The consequences of increasingly stringent environmental emission controls.