How does a VI improver thicken at high temperatures but not thicken at low temperatures?
A.. VI (Viscosity Index) improver can be thought of as a very long string which at low temperatures is tightly coiled into a small ball and floats suspended in the oil with little effect on the viscosity of the oil. At high temperatures this ball expands and uncoils and encloses a much larger volume of oil within its structure. This effectively prevents the oil from thinning because of the greater volume taken up by the expanded balls of VI improver molecules. 6.Q..
