There is definitely some marketing hype involved by manufacturers in order to advertise certain specs where they will say a vehicle “requires” a certain Octane fuel. The truth is that most don’t really “require” it unless you need to get every last ounce of performance out of the vehicle. Generally the differences are not nearly as great as they would lead you to believe and the percentage of performance gain not as great as the percentage of price increase.
My bike “requires” mid-grade (89), but I have never been able to tell any appreciable difference between 87 and 89 in terms of performance. I know there isn’t that big a price difference between regular and mid (about .10) when you are only putting in 3.5-4 gallons on average. But why pay for it when you don’t need to?
Putting in higher octane than your vehicle requires can at best have no affect whatsoever and in some instances can actually cause adverse performance. But if your bike requires 87 and your putting in premium chances are your just pissing away .20 a gallon.
USA Today had a good article on fuel octane and performance many years ago…
http://www.usatoday.com/money/autos/2003-07-30-premiumgas_x.htm