A method is disclosed for improving fuel economy in an internal combustion engine. The method may involve sensing a temperature of an engine block and determining a block thermal energy representing an ability of the block to reject heat. An open loop control scheme may be used together with the block thermal energy to predict if a coolant in the block is about to enter a boiling condition and, when this is about to occur, to open a block valve to permit a flow of coolant through the block. A closed loop control scheme may be used together with the sensed temperature of the block to determine if a coolant boiling condition is about to occur, and to control the block valve to permit a flow of coolant through the block which is just sufficient to prevent the onset of coolant boiling in the block.