I use premium in my vehicles for the same reason that some of the high end outdoor power equipment manufactuers are demanding that premium be used in their products. It is not so much for the octane, but the level of detergents and other additives. The major oil co.'s have cheapened up so much on the additives on regular gas (charge more and cut quality, sound familiar?) that I now use the premium to help prevent injector/valve/carbon deposits. Even though I still add a Techron type cleaner to a tankful before each oil change, I'll spring the extra $ for the premium. Cheaper and easier than a motor/intake carbon flush.