One of my mates owned a fuel injection business, and higher octane fuels have a cleaner in them that keeps injectors healthier. if you feel standard unleaded and High Octane (98)in Australia, the High Octane will feel "soapier" or smoother.
I have always used 95+ in my Morgans.
He also commented that "Green" diesel was a fuel injection companies best friend as it stuffed up fuel systems far faster than standard diesel.
