Gin over the engine, never heard of that one before! I suppose if you were to use even a regular 'Tanq' you could end up with a engine a la flamber!
I have always subscribed to the ritual of 'Malvern Water' on the Rad cowl badge. It seems to have been well received by the 'Ancestors'; it also ensured that the gin went where it was appreciated!
Haven't been to a LMC for some years, and now it's virtually in my 'Back Yard', I intend to take advantage of the fact.