What can be a consequence of using low-grade fuel in an aircraft?

Using low-grade fuel in an aircraft can lead to reduced engine efficiency and potential power loss due to the fuel's lower combustion properties. Aircraft engines are designed to operate optimally with fuel that meets specific grade and quality standards. Low-grade fuel may not ignite as efficiently or burn at the appropriate temperatures required for optimal performance. This inefficiency can result in incomplete combustion, leading to a decrease in power output and an increase in engine wear over time. When the engine does not perform as intended, it can have adverse effects on overall flight performance, including reduced thrust and fuel economy, making option C the correct choice.