Don't waste your money. Octane is a measure of the fuel's resistance to knocking or pinging. Only high-compression engines (think sports cars) need the stuff. The folks who wrote the owner's manual know what they're doing; if they say regular is OK, then regular is OK!!

I recently read somewhere that only ~5% of all cars in the US need premium gas. IMHO, if that number drops much further we'll see premium phased out, as there won't be enough demand to make it profitable. Those who still drive high-compression cars will then have to put an octane-boosting additive in each tank.