I just got the free oil change/tire rotation on mine (one of two that came free since it's certified). In fifteen months the oil life dropped from 57% the day I bought it to 43% when they changed the oil. Now it's at 100% oil life
I also filled up the tank the other day for the first time in a long while, hopefully it'll last to the end of the year.
I'm sold on the Volt and have no real complaints, and in a year or so I plan to trade it in for a newer one.
Enjoy! It's an awesome car, way more fun to hypermile than my Insights were