Paper: Slow Speed Engines

The horizontal type internal combustion engine evolved very naturally within the oil industry and it is, next to the steam engine, probably the oldest type prime mover in continuous use in the field. Since the Otto, or four-stroke cycle had already been established, the early engines followed this, and from an effort to reduce weight and moving parts evolved the two-stroke cycle engine. So today we have the four-stroke cycle and the two-stroke cycle engines in general use in the oil fields.