Final answer:
Aircraft engine oil must have balanced viscosity to provide proper lubrication in cold and hot temperatures, and it should have high thermal stability to withstand the extreme heat without degrading.
Step-by-step explanation:
Two important characteristics of aircraft engine oil are its viscosity and the ability to maintain lubrication under a wide range of temperatures. Viscosity is crucial because it determines the oil's ability to flow and lubricate engine parts. Aircraft engine oil must have a high viscosity at low temperatures to ensure it can still lubricate the engine during a cold start, and it must not become too thin at high temperatures to continue providing effective lubrication in the engine's hot environment. This balance is typically achieved through the use of multi-grade oils that include viscosity-modifying additives to maintain optimal viscosity across temperature ranges.
Another characteristic of aircraft engine oil is its thermal stability. The oil should not break down or change its properties significantly at the high temperatures encountered in an aircraft engine, as these could lead to a loss of lubrication and potential engine damage. Advanced aircraft engine oils are designed to withstand the high thermal stresses and minimize deposits and sludge formation, contributing to the engine's reliability and longevity.