filled up on normal unleaded is there a fuel additive i can use
cheers

 

octain booster although adding it after filling up the tank the mix prob wont be very even.

You may get away with just running it steady and not boosting it while you use the tank, personaly i'd get the tank as low as you dare, fill it up with vpower, get it as low as you dare then refill it before even thinking about.

other option is get a jerry can of vpower and just drain the normal stuff out and put the vpower in.