If contaminated lube oil were allowed to settle undisturbed in a tank, into which layers would the contaminants separate?

Correct Answer: Option C — Sediment on the bottom, water in the middle, and oil on top.

Gravity separation of contaminated lube oil relies on density differences. High-density sediment settles to the bottom, intermediate-density water forms the middle layer, and lower-density clean lubricating oil floats on top.