Silicone oil, a step or two up from Armorall (at auto parts store). You must lubricate rubber motors to get their full power, and keep them from breaking when fully wound. Sil-Slick is seriously greasy stuff! Consider wearing disposable latex gloves when lubricating motors. Put some Sil-Slick in a zip-lock poly bag with your cut-to-length motor and let it soak. Put on the O-ring and tie the knot BEFORE lubricating!