I've used & measured high octane fuels on several cars over the years.
& it's definitely a "horses for courses" experience.
Most of my car journeys are 15-20 miles. So the one time I do use high octane fuel is when I go on a long trip, even in a car that normally doesn't benefit from high octane fuel. It gives the cleaners time to do their work, and the payback lasts for months.
For example, I can't imagine what the previous owner of my Saab was doing to get 33mpg... in my normal driving that figure rose to 37mpg: high octane fuels don't seem to make a difference in my normal motoring.
And after 2 seven hour runs to & from Scotland on high octane fuel, that number's now 'cleaned up' to over 41mpg.
The message here would seem to be to go for a good long (very long) drive every so often - you'll save fuel in the long run!
Will
