Is "last month" currently "June 2012" or is it June 18-July 17?
Last Month is really the last 30 days. So it would be June 18-July 17.
Is there any way to have rollup stats for all vehicles...
No, we don't have any sort of combined stats across all vehicles. That's something we've been thinking about. I think it would be a useful addition to provide some of those on profile pages.
The whole point of using Fuelly though is that it calculates and summarizes useful stats for you...
I agree, and we provide a bunch of useful stats. Check out the Cost Analysis stats and the timeframe shifting that MMUK mentioned. We just can't provide every potential stat that someone wants.