Must be an international thing. In my country as well the act of "oiling gears" means giving bribes in order to obtain something and/or speed up the process by having your papers put on top of the pile.

I'm German (born, raised and lived in Munich) and I do not associate "Läuft wie geschmiert" with bribe. To me it has only one meaning, which is "running smoothly". In this context I'd guess the person said that Linux runs smoothly and from a technical point of view there is no reason to switch to Windows.