Just thought I'd pop back in with another update. The Volt told me it was time to change its oil, so I changed the oil for the first time this weekend. Its been 16 months and 38k miles, 73% of that has been on electric. This is still my favorite car I've ever driven on a daily basis. So far, all I've done is this oil change, rotate the tires, and added some windshield washer fluid. It is fantastic.