Hi Edo.
WD40 comes in a spraycan, and gets sprayed all over the car.
In some cases it makes the plasticchassis become sloppy, so the motor and bearing can pop-up. In all cases its makes a mess.
If you spray it in a cup, and then puts it in/on the motor i guess its ok, have never tried.
Use thin oil to oil the motor (put an amp.meter on the motor when you run it at 3V, look at the difference when you use different kinds of oil, and watch the difference in A).
Excelerant, hard to translate.
In Danish its called Rense Benzin, a direct translation is Cleaned Gasoline, does that ring any bells ?
Its that chemical you can use for removing Contact-glue from surfaces.
Maybe its just called Benzine or Benzene ?