I don't think a higher octane fuel is necessary unless your car knocks when you use a lower octane fuel.

The FTC says that, for the most part, it's not worth the extra cost:

http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

The FTC does say certain cars specify it, but from all I've read you should try to get away with the lowest octane you can. By that I mean, if a lower octane fuel does not cause your car to "knock" then you can use it. Otherwise, the higher prices are just a ripoff.

It's possible that your car needs it, but you won't really know until you try giving it lower octane.

And higher grade fuel will not make your engine last longer or run cleaner. It's all about the knocking.