I am actually an engineer at an Oil refinery. This is a quote directly from the experts, "Many high-performance engines are designed to operate with a high maximum compression and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power."
Technically, this is a quote from Wikipedia, not directly from the experts, but the experts, Chemical process engineers, agree with this.
At the end of the day, do not use more expensive gasoline unless you need it.