Ok to straighten out a few misconceptions
you will not lose power or mpg by uising a higher ocatance ,as you drive a car goverened by a computer and fuel injection not a carburator
this means the ecu will change the timing to adjust for lower and higher octance, meaning if you have used cheap gas for its whole life you will now have higher burn temps which will be clearing out the carbon build up but it is not instant either. it will take a few tanks to notice a difference in a car with large deposits, this will also lower your inital data recoreded from changes in fuel usuage as the carbon create hot spots with the higher temp which will cause a slight timing retardation until it is retified by it blowing the carbon out to a poiint, which is hard unless you get a motorvac to thoroughly remove it.,
I have air fuel ratio meters in both my cars as well as a pyro which monitors the burn temp precisley,by reading this it shows me th temps rise much better with 94 ocatne as well as much better than any crap gas shell sold me for 5 years before i switched for the better.
So all in all if you can get 600++km a tank consistanly like mine with 1000lbs added with modifications and stereo dragging around on top of it with chrome 18's then make an argument that 87 is better but everything i have learned and seen in my personal test come back with positive results every time i fill up my tank.
using a higher octane allows your ecu to make a descion on how much to !Removed! or advance the timing according to the needs of the driver not its limitations of knocking which will never be felt by a driver since the knock sensors are way to sensative and respond faster than you can think you heard a knock.