Gents, I have a 2015 Chevy Volt. This car has an engine and a large battery. Runs as a full electric until the battery goes flat. Then, it fires up the engine and operates very much like a Prius. About 80%-90% of the miles are all electric, so the engine (and the oil contained therein) is hardly used. When it is, it's because we were on a road trip, so the engine warms up fully and burns off any condensate. GM calls out Dexos 1. Mobil 1 Annual Protection meets Dexos 1. GM's Oil Life Monitor tracks both engine use, and calendar time. It will not let the oil go for more than 2 years in the sump. GM says that any Dexos 1 oil can last up to 2 years, depending on engine use. Mobil says that their Annual Protection oil must be changed out after 1 year, no matter what the engine use. Who's right?