Microdieseling: The Explosions You Never Hear

Industrial reliability relies heavily on the integrity of machinery lubricants, yet numerous degradation processes remain invisible to the naked eye. In the latest installment of WearCheck's ongoing technical series, "When Good Oils Go Bad," technical manager Steven Lumley examines the mechanics of microdieseling, a severe form of pressure-induced oil degradation. The discussion highlights how entrained air bubbles inside lubrication and hydraulic systems can transform from passive contaminants into aggressive catalysts for system failure under rapid pressure fluctuations. To illustrate the destructive potential of collapsing bubbles, Lumley draws an analogy to the pistol shrimp, a marine creature capable of generating cavitation bubbles that briefly produce temperatures hotter than molten steel. Within industrial machinery, a comparable phenomenon occurs thousands of times per second when air pockets become trapped in oil subjected to high pressure. As the pressure rises faster than heat can dissipate—a process known as adiabatic compression—the internal temperature of the bubble can soar past 1000°C, causing the surrounding oil to effectively undergo microscopic combustion. Microdieseling poses significant operational challenges for heavy industries reliant on continuous hydraulic and gear performance, such as mining and large-scale manufacturing. The continuous cycle of microscopic explosions generates extreme local temperatures, shockwaves, and micro-jets of oil that erode metal surfaces. Over time, these micro-events lead to severe surface pitting, valve sticking due to varnish deposits, and sluggish system response as the oil loses its structural integrity and pressure-transmitting capabilities. Experts emphasize that microdieseling is fundamentally an air-management issue rather than merely a failure of the lubricant itself. Mitigating the risk requires rigorous maintenance practices focused on preventing air entrainment, managing reservoir designs, and el