Of the large farm sprayers, combines, skid loaders etc. many have hydrostatic drives and they all are less efficient than gear drives or electric drives. The reason they use hydrostatic drives is for precise control of ground speed without changing engine RPM. The first prototypes of electric drive sprayers are being unveiled at machinery shows and they are more efficient than hydrostatic. But also heavier and more expensive. The most efficient drive train at present is the diesel electric locomotives. The most efficient farm tractors presently achieve about 17 hp-hr/gal. of fuel at the drawbar, which takes into account drive train loses. We are a long way from that in cars.
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