[Kid]

He's injecting it straight into the propane bottle to provide a more consistent amount of silicone to each fill and make it so it is not necessary to oil so often.

Madmax had a prototype that did exactly this (worked extremely well), but never marketed it because it was dangerous (people could inject other things which may not react safely).

edit: it works with Green Gas, the oil doesn't all shoot out at the beginning. Green gas = propane + silicone oil. (sometimes just pure propane)