[davebslater(uk)]

shell will sell you 102 octane fuel , since thast what the WRC cars use and is made specifically to be very knock resistant . Of course you have to buy it in 25 litres and you end up with loads of containers hanging about . 102 octane is actually the highest octane the FIA will let you use .

of course , if you have a handy pharmacutecal company nearby , you can simply add some toluene to the correct octane you would like , toluene though exists inlots of things like cellulose thinners and even in electrical contact cleaner .

Since petrol contains toluene you are not in fact damaging your cat with it .