Which of the following is NOT a factor in establishing the maximum compression ratio limitations of an aircraft engine?

The correct choice highlights that the type of oil used does not play a direct role in establishing the maximum compression ratio limitations of an aircraft engine. Maximum compression ratios are influenced primarily by factors that directly affect combustion and engine thermodynamics.

Detonation characteristics of the fuel used are critical because different fuels have varying abilities to withstand compression before igniting spontaneously, which can lead to knocking. Higher compression ratios often require fuels with better anti-knock properties to prevent detonation.

The degree of supercharging is another important factor since supercharging increases the amount of air (and consequently oxygen) entering the combustion chamber, allowing for a higher compression ratio and more efficient combustion. However, supercharging must be carefully managed to avoid detonation.

Design limitations of the engine encompass the structural strength of components and thermal properties, which determine how much compression can be applied without risking damage or failure of the engine parts.

In contrast, the type of oil used mainly affects lubrication and cooling rather than the fundamental combustion processes or structural integrity related to the engine's ability to handle a specific compression ratio. Therefore, it is not a determining factor in setting maximum compression ratio limitations.