A windrower has a hydrostatic header drive system with a header drive pump and one or more header drive motors. The windrower also has a chassis with wheels coupled thereto, an engine, and a ground drive system coupled to the wheels and the engine. A control system has plural sensors having first, second, and third sensors, wherein the first sensor monitors engine load, the second sensor monitors hydrostatic header drive pressure, and the third sensor monitors ground speed. The control system has one or more controllers configured to receive input from the plural sensors, compare the input with respective target values for engine load, header drive pressure, and ground speed throughout a range of ground speeds defined based on an operator configured maximum ground speed, and automatically adjust the ground speed based on the comparison.