Steam rail locomotives were highly inefficient, as toward the end of their era 6 percent efficiency was considered excellent. Therefore, every imaginable fuel-saving scheme was tested. One such scheme was compounding, sending the exhaust steam from a high-pressure cylinder to do more work in a larger low-pressure cylinder. In marine engines, it was relatively easy to place three such compounded cylinders on a common crankcase, presenting relatively easy plumbing from high-to-medium to low-pressure cylinders. When applied to locomotives, whose cylinders are necessarily located where they can directly drive the wheels through crosshead and side rods, the added compound plumbing added flow and expansion losses. Trying for a maximum fuel savings with three stages forced placement of the third cylinder under the boiler, driving a crank axle between drive wheels. This, by limiting service access, increased the labor cost of keeping such locomotives on the road enough that fuel savings were eaten up by increased maintenance.