my son had a Ford Focus ST with water methanol injection. It works best with turbo or supercharged engines as it both cools the air/fuel charge mix and raises octane value, allowing higher boost pressure.
As an aside it also lowered exhaust gas emissions to the point the car still met MOT requirements with the catalyst removed, probably because the water/methanol improved burn efficiency.
Water methanol injection was used extensively in the supercharged aircraft engines from the early 1940s, along with in Germany, nitrous oxide injection.
The Brits, with up to 150 octane fuel available, didn't need nitrous and made less use of water methanol.
