So what’s the technical reason for strictly observing the correct lubricant levels in engine, gearbox and differential sumps?
“When the sump level is too high, the oil can be churned and aerated by the moving components, leading to air entrainment…and air contamination warrants immediate attention.”
Here’s the crunch: “Air has no load-bearing capability and when compressed, air creates tremendous heat. For a machine serviced by an oil bath, the collapse of the oil film as bubbles pass through the component interfaces causes surface wear and destruction and sets components on a path to failure. For circulating systems, as an air bubble passes through the pump, the bubble is compressed to system pressures. As the bubble collapses, it creates enormous heat, potentially causing flash vaporization of the oil around the super-heating bubble.” Phew! And you thought you were building in a safety margin by overfilling.
