A system for replenishing a source of pressurized fluid for use in driving the wheels of a motor vehicle includes an accumulator containing fluid at relatively high pressure; a reservoir containing fluid at lower pressure; an engine driveably connected to the wheels and having a variable torque output; a pump/motor driveably connected to the wheels, including an inlet and an outlet, and having a variable volumetric displacement for pumping fluid between the accumulator and the reservoir; and a controller for determining a current cruise charge pressure limit for the accumulator, determining a desired magnitude of pump/motor torque with which to pump fluid to the accumulator, determining a desired magnitude of engine torque with which to drive the pump/motor at the desired magnitude of pump/motor torque, and controlling the engine to produce the desired magnitude of engine torque, to drive the pump/motor in a pumping mode at the desired magnitude of pump/motor torque, and to pump fluid to the accumulator from the reservoir.