Are you sure that you smell lubricate oil or is it possible that your heater's radiator is leaking (familiar problem with the W201) and you are smelling coolant (since your car is loosing coolant...)?
The switch is for (de)activating the power window switches in the back of the car. Switching to the dot (person visible) will deactivate the switches in the back and switching to the person (dot visible) will activate the switches in the back. When the switches in the back are deactivated the switches are (probably) not illuminated.
with a minor 600+k