Commercial Pilot License (CPL) Practice Exam

During engine break-in, mineral oil is commonly used because it provides a favorable environment for the initial wear-in process of new engine components. Mineral oil has a composition that allows for effective seating of piston rings and helps create the necessary wear patterns on engine surfaces. Additionally, its natural lubrication properties help in maintaining adequate oil film strength under varying temperatures and pressures, which is crucial during the break-in phase when components are not yet perfectly fitted.

Other types of oil, such as ashless dispersant oil, synthetic oil, and detergent oil, are typically not recommended for initial break-in. Ashless dispersant oils are designed to prevent sludge build-up and may not provide the necessary friction characteristics during the break-in process. Synthetic oils have superior high-temperature performance but can sometimes lead to insufficient wear during the crucial initial hours of engine operation when parts are still mating together. Detergent oils, on the other hand, are formulated to keep engines clean and may not offer the same benefits for new engines undergoing the break-in period.