[chuckles]

......."Actually, water injection just boosts octane"......

I don't think water has octane. It does, however, cool the cylinder, which alows a leaner mixture without ping. It also adds power by the steam formed. If your car pings, (unusual today with knock sensors), You might try a cooler thermostat, say 160 deg.

[Doctor Stochastic]

You're correct, water doesn't contain iso-octane (2-2-4 trimethylpentane) but it acts similarly in that the water scavanges the free radicals that cause premature detonation. So does tetrethyl lead and iron carbonyl (ugh, European usage) and tri-cresyl phosphate. Water adds no power in iteslf (it's already burned.) Water does allow higher compression.

I'm using "octane" to mean anti-knock properties rather than the percent iso-octane in the mixture.

Technical note: originally, the "octane rating" of a gasoline was the percent iso-octane in a mixture of iso-octane and n-heptane that knocked the same amount (measured by an engine with a knock-meter) as the test gasoline. With better anti-knock compounds, and "octane rating" of over 100 is possible. The definition has been changed over the years. (There's also the instant measurement and the average measurement, just to keep things complicated.)