My oil is down to 5%, per my Volt, so I've been trying to decide where to have it changed. My Chevy dealer is a 20-minute drive away and advertises an oil change, etc. deal that includes ACDelco dexos1 Full Synthetic. My local garage, that I've used for years and trust, says they always use whatever the manufacturer specifies and it will be dexos1, but not full synthetic (unless I'm willing to pay a lot extra). And the Volt's manual actually says "ACDelco dexos1 Synthetic Blend is recommended" -- emphasis on "blend", not "full synthetic". So please help me out here: should I demand "full synthetic" or "synthetic blend" or just be happy with dexos1?