Contrary to popular belief, not all 2-cycle engines are suited for the same purposes. For the most part, 2-cycles can be separated into two distinct groups: water-cooled engines and air-cooled engines. Outboard motors are typically run at high speeds for long durations and then throttled down once a boater reaches his or her destination. Recirculated water keeps these engines cool. On the other hand, most chainsaws are stopped and started frequently, and their engines are air-cooled.
In automotive terms, the outboard motor can be likened to a country car engine – speeding along with minimal interference. The chainsaw motor is more akin to a city car that makes multiple pits tops. Not surprisingly, these very different beasts require different oil formulations. Outboard motors operate best when treated with heavy base oils that don’t evaporate quickly. Evinrude XD50 oil, for example, is specially designed for use in watercraft. Chainsaw motors require lighter base oil with detergent additives. In an outboard engine, these additives would leave destructive ash deposits. However, the chainsaw’s vibrations serve to knock these deposits out of an air-cooled engine.