CORROSION - 1

A petroleum oil that is new or kept clean by proper filtration is generally non-corrosive and will provide good protection against corrosion caused by the atmosphere. However, inside an engine oil oxidation by-products will attack internal engine steel and bearing materials that are typically manufactured aluminum, copper, lead and tin (a lead-tin flashing is used for break-in purposes on the few engines that use aluminum rod and main bearings). Most gasoline and diesel engines use copper-lead main and connecting rod bearings. Water present due to condensation caused by temperature and humidity changes or short stop and go driving where the engine never reaches the proper operating temperature, although still hotter than the ambient temperature, can also cause corrosion. The hotter the oil is when water is present the more severe the chemical reaction is and corrosion related damage could definitely occur. In addition, water present in an oil for an extended period of time can emulsify the oil and form a mixture which is much more corrosive than the two components alone and can then form sludge which may block oil filters or small passages.