Nah not at all, Have paid upto $1.46 for premium the other week! But what you said is like finding $5 in your bedroom and going "sweet i'm gonna go drive to the servo and put $5 petrol in and drive home" Pointless........
But yeh as Joel says, its what your car is tuned on is whats best for it, But a regularly used servo is also the key, the fresher the fuel the better for it, besides the cops use Mobil, so thats outa the question....