Oil Change and Spark Plugs Question

[911monty]

While the maximum oil is in the sump when it has been sitting cold, I believe the intent of hot oil is to circulate any heavier debris/contaminants back into the oil that have separated and settled into the bottom of the sump where they can then be removed when the oil is drained. Since the heavy materials are on the bottom they tend to resist flow and remain in the sump.