My Kawasaki ZX14 has 12.0/1 ratio and I run it on 87oct pump gas, when it gets real hot (95+) here I will bump up a grade to 89/90 depending on the station (also for the record, it run 9.50 @ 146 in the 1/4 mile in street trim). My ZX12 that I sold ran 12.5/1 and I ran it on 87 pump gas (Best pass with a slick and bar, 9.22@145). Unless it knock when riding/driving it hard use the lowest oct rating that you can for the best performance out of the engine. If your using a higher oct than the engine needs your wasting money.