Contrast the use and performance of a 5W-30 motor oil with a 20W-50 motor oil.

Correct Answer:

A 5W-30 motor oil flows more easily during cold starts and is thinner at normal operating temperature than a 20W-50. The 20W-50 is thicker, including when the engine is cold, and provides a thicker oil film at operating temperature. Use the grade specified by the vehicle manufacturer, since the appropriate oil depends on the engine and operating conditions.