No it's not mandatory just cost effective. You can retard your timing and have less power and less mpg but run 87 octane fuel. Or you can premium fuel and get more power, more detergents to kept injectors clean and better gas mileage.

That's just what I have heard I have never tested it but others have. The way I look at it premium has never been cheaper in comparsion to 87 octane. Remember back when regular was a dollar and premium was a $1.20 that's was a 20% premium. Now regular is $3.37 and premium is 3.65 that's only a 7.7% premium a real bargain.