[Jonster]

I was under the impression that the higher octanes only make a difference if you are really driving the car hard. (and also helps lengthen engine lifespan)

edit: Obviously putting 91 in SS/ZL1 minimum and 87 in LS/LT minimum

There are also many other factors when fueling up like brand and region. There are some articles on Shell V-power vs BP ultimate, but gas is different based upon region as well.

(Not sure if this helps, just spitting out some knowledge)