In a diesel-powered highway truck at operating temperature, which of the following is true about coolant temperatures compared to lube oil temperatures?

In a diesel-powered highway truck, when the engine is at operating temperature, the correct understanding is that coolant temperatures run cooler than lube oil temperatures. This is because the engine's lubricating oil is designed to operate at a higher temperature to ensure proper lubrication of the engine components, which reduces friction and wear.

The engine coolant, on the other hand, circulates through the engine and is used to absorb heat. Its primary function is to maintain engine temperature within a specified range to prevent overheating, which means it typically operates at a lower temperature compared to the engine oil.

This temperature difference allows the coolant to effectively perform its role in thermal regulation, preventing the engine from reaching excessive temperatures while the oil ensures that engine parts are adequately lubricated at optimal performance levels. Understanding this temperature relationship is crucial for diagnosing engine performance and troubleshooting potential cooling or lubrication issues.