[Dave Samson]

We have no problems buying Optimax (Premium unleaded) which Shell claims to have an 98 octane rating for around 10% higher price than regular unleaded of 92/93 octane.
I ask what's the point of taking the considerable risk of messing around with these additives when 98 octane fuel is available at the pump ? Of course if you want to achieve > 100 octane, an additive is required.
I have been running this fuel for the past year or so since it has been available as do many other Cobra nuts down here. I guess the advantage of EFI coupled with a knock sensor takes care of fuel irregularities.