What tool is essential for measuring the temperature of an engine?

The essential tool for measuring the temperature of an engine is a thermometer. This instrument is specifically designed to provide accurate temperature readings, which are critical for monitoring engine performance and ensuring it operates within safe temperature ranges. Maintaining the correct temperature is vital for preventing overheating, which can cause severe damage to engine components.

Other options, while valuable in their own right, serve different purposes. A pressure gauge measures the pressure of fluids within the engine system, such as oil or coolant, and is not equipped to assess temperature levels. A multimeter is primarily used for measuring electrical parameters such as voltage, current, and resistance, rather than temperature. An oil tester evaluates the quality and condition of engine oil but does not provide temperature measurements. Hence, a thermometer is clearly the appropriate choice for monitoring engine temperature effectively.