Question for those of you living in the flat parts of the US. For driving across Kansas, Illinois, and Indiana on I-70 in an ECO MT, what octane would you recommend? Basically I'm going to be sitting on Cruze control for hours on end. Central Missouri is hilly enough that I'll run 91 or higher depending on what's available. Northeast of Columbus, Ohio I'll run 91 or higher to handle the hills of the Appalachian mountains.