There seems to be a lot of information circulating about Dexos, so I wanted to cut through it to summarize what it is and what the impact will be. The term Dexos was created by GM as a classification for the oils required to be used exclusively in their vehicles. The Dexos classed oils are formulated from high grade base stock oil which would typically be used in a semi or full synthetic oil. The oil is designed to increase drain intervals and improve fuel economy. At this time there are two options: Dexos 1 or 2. Dexos 1 is formulated for gasoline engines and 2 is for diesel engines.
The impact to car owners is a more costly oil change and you will need to verify with the service centre that they carry a Dexos approved oil. Service centres will have to create more room for Dexos approved oils in usually limited spaces already. The major impact will be on refiners who will have to obtain licenses and pay royalties to GM for the production of the product. Dexos 1 and 2 oils have rolled out and are readily available from a number of different brands. Follow this link to a list of companies carrying Dexos http://www.gmdexos.com/licensedbrands/dexos1licensedbrands.html.
The lube industry from manufacturers to service centres are still weighing in on whether Dexos will be here for the long term. For the time being, it is here and GM vehicles recommending Dexos approved oils will require the use of them to avoid voiding the engine warranty.