I just had the oil changed in my Volt a few days after its 2 year mark with around 14,000 miles in hybrid mode out of a total 38,000 miles (I forgot to write down the exact mileage numbers). The oil lifetime computer display still said it had a bit over 30% of its usability remaining. I suspect this is because I mostly use the engine on the highway for 15+ mile segments. My impression is that oil life is shortened by lots of brief cold starts and short driving distances typical of city driving.
This is hogwash. Or mostly. Yes, power in the afternoon can be more expensive, if you live/work in an area that has Time of Use metering. The amount of power required to recharge this car will not have a huge effect on the grid. Over time, yes, it may become a bigger issue as more cars need to recharge during the afternoon, but I'm willing to bet that things like A/C, lighting, and computers, have a much bigger impact on the grid.
the point wasn't about $$$ but rather about "costs" to the grid and the environment. regardless, yeah, this mainly applies to summertime.