Yes there is. I don't recall the specifics but a Google search will bring it up for you I'm sure. I also seem to recall that, although the calculations and ratings are different the Euro gas still ends up being a point or so higher than what we get here.

As for which fuel to use - if the manufacturer states premium then I use premium. Using anything lower has the potential for reduced performance and possible pre-ignition. One is less fun, the other is just not a good thing. On the other hand, if the manufacturer recommends regular there is nothing to be gained by using a higher octane, unless you detect pre-ignition.

Oh, and when I filled up the other day I paid $38.18 for 12.645 gallons: $3.019/gallon. I had filled with regular at the same station for the $2.859 price I would have paid $36.15 for the same 12.645 gallons. I will gladly spend the extra $2.03 to prevent a loss of performance and the potential damage from pre-ignition. I'm sure most, if not all, of us collect that much loose change through the course of a week anyway.