Which of the following tests is not typically used to assess fuel metering system performance?

The engine oil viscosity test is not typically associated with assessing the performance of fuel metering systems. Fuel metering is primarily focused on the delivery and management of fuel to the engine, which is crucial for optimal combustion and efficiency. Evaluating fuel pressure, cleaning fuel injectors, and monitoring the air-fuel ratio are all essential practices that directly impact how the fuel system operates.

Fuel pressure tests ensure that the system is delivering the correct amount of fuel at the right pressure, which is critical for engine performance. Injector cleaning helps maintain the injectors' efficiency and prevents blockages that could alter fuel delivery. Monitoring the air-fuel ratio is vital in ensuring the ideal mixture for combustion, which affects emissions and engine performance.

In contrast, an engine oil viscosity test pertains to the lubrication system and involves assessing the oil's ability to flow at different temperatures. While engine oil is important for overall engine health, it does not influence the fuel metering system's operation directly.