Oil Aeration in High Speed Combustion Engines

Modern passenger car engines are designed to operate at increasingly higher rated engine speeds with more internal parts (multi-valve engines) requiring lubrication. There is a higher probability for the oil quality to deteriorate due to an unfavorably high level of oil aeration. The high oil aeration can cause hydraulic lash adjuster misfunction and connecting rod bearing failure.

This paper presents results of recent research and development work concerning the occurence of oil aeration within the lubricant system of modern combustion engines. In particular, the work has concentrated on the following:

• How oil aeration affects engine operation
• How cavitation occurs in the supply bore to the connecting rod bearings
• What causes air entrainment in lubricants