It seems like it would be outstanding PR if volt owners had a common place they could track their mileage. I'm not necessarily talking about daily but perhaps weekly (with daily as an option or rolled up to a weekly/monthly).
I like Lyle's and would think it should be KISS so that non-owners (rem PR) can see and *quickly* understand it and see the benefit and practicality of owning a Volt. Only think I'd add to Lyle's would be # times charges (else misleading as it can be misinterpreted as a one/day charge geting that many miles.) and outside avg temp that day.
Ideally it would be on this site but there may be some other place on specialized mileage forums, etc.
This chart has a nice feature of $cost per mile for gas.