Lubrication Systems What is the primary purpose of the hopper located in the oil supply tank of some dry sump engine installations? a. To reduce the time required to warm the oil to operating temperatures. b. To reduce surface aeration of the hot oil and thus reduce oxidation and the formation of sludge and varnish. c. To impart a centrifugal motion to the oil entering the tank so that the foreign particles in the oil will separate more readily.