Folks need to log their cars to see firstly is any timing being pulled/knock retard detected to determine IF running higher octane fuel has any value. If so, sure, premium may clean that up or even running a few gallons of E85 to clean up the timing but you take a slight hit in mpgs but it's cheaper so probably still saving money. It's almost always cheaper to run 87 b/c the slight performance improvement/efficiency in engines that gain from running higher octane fuels will never offset the cost per gallon increase. Disclaimer is of course this is for vehicles rated to run a min. of 87. Butt dynos do not count - it's a data-driven discussion.