alexibrow wrote: When I bought it, fuel economy was between 45-50mpg, but once I'd run a few tankfuls of Shell Optimax through it to un-bung the carbs/valves etc, there was a marked improvement.

I was checking out bp ultimate and optimax and reading quite a bit on it, and am now feeling very tempted to use a few tanks of super unleaded to clear up internals... do you get a difference in performance as well? or do you just notice in your wallet?

I noticed an immediate increase in performance with the premium 97RON fuel, but I expect this is due to the detergents in the fuel cleaning the internals rather than anything else. When I reverted back to 95RON cheapo stuff, the performance and economy didn't change immediately, but it's just now beginning to feel a little slower after roughly a dozen fill-ups. Sadly I won't get to put any more premium stuff in to see if there's an improvement again, as I've just sold the bike today...

The plan was to put a full tank of 97RON premium fuel in every now and then, just to see. Anyone else done this?

not that it counts at all toward this topic, but i fill up with premium ever 3rd tank during the winter to help with carb icing on the ZX6. you can notice it starts easier in the cold mornings