According to Edmunds.com, Dexos1 is an oil blend that General Motors created for gasoline-powered vehicles, and Dexos2 is the blend GM developed for use in its diesel engines. These Dexos oils were introduced by GM in 2011 as new mixes designed to maximize the efficiency of the company's vehicle motors.
Due to advancements in engine complexity, GM created the Dexos oils to maximize fuel efficiency and to increase engine life, Edmunds.com states. As engines' oil quality improved, so did requirements to provide greater performance and handle higher temperatures. The Dexos oils are specialized blends that GM recommends for use in its vehicles.