Where is fuel typically sampled from in the Cessna 172?

Sampling fuel from the fuel selector and strainer in a Cessna 172 is a vital procedure to ensure the quality of the fuel before flight. This location is key because it provides a representative sample of the fuel available to the engine, allowing for the detection of contaminants such as water, dirt, or sediment that might have settled in the system.

By sampling from the fuel selector, pilots can check the fuel being directed to the engine during operation. Additionally, the strainer serves as a filtration point for fuel before it enters the engine, which is crucial for maintaining optimal engine performance and safety.

Sampling from the fuel tank cap may not yield a reliable assessment since contaminants could be found further along the fuel delivery system, and sampling only from fuel lines could miss issues present in the tank itself. Moreover, the mention of sampling from just one spot in the auxiliary tank doesn’t account for the need to assess fuel from all potential areas where contamination could occur. Thus, sampling from the fuel selector and strainer is the most appropriate and effective method for ensuring clean fuel is being utilized.