The pistons in car engines rub up against their cylinder walls thousands of times a minute; without lubrication in the form of motor oil, they and other parts of the engine would quickly wear away, causing engine failure. Motor oil contains chemical additives that extend how long engines can run without failure, but, despite decades of ubiquity, how such additives actually work to prevent this damage have remained a mystery. Now, engineers from the University of Pennsylvania and ExxonMobil have teamed up to answer this question. With a vested interest in the chemistry and performance of lubricants, scientists at ExxonMobil worked with scientists at Penn whose research focuses on nanoscale measurements of friction and lubrication. The team conducted research to probe nanoscale properties and mechanisms of lubricant films and ultimately uncovered the molecular mechanisms behind a common anti-wear additive.