Excessive cylinder head and engine oil temperatures can occur due to which of the following?

The correct choice relates to excessive cylinder head and engine oil temperatures occurring due to low fuel grade usage. When a pilot utilizes a lower-than-recommended fuel grade, the fuel may not combust efficiently, leading to incomplete combustion and higher operating temperatures. Specifically, lower-grade fuels can increase the risk of knocking or pre-ignition, both of which can generate excessive heat within the engine.

Using a higher grade of fuel generally helps prevent knocking, thereby ensuring smoother combustion and keeping operating temperatures more stable. A rich mixture setting typically helps cool down the engine as it provides more fuel relative to air, which can absorb more heat during combustion. Cold operating temperatures usually lead to lower service temperatures, which is contrary to the scenario posed in the question. Understanding these dynamics is essential for maintaining optimal engine performance and preventing overheating issues.