I've never used any lubricant on the extruder and haven't had any problems with. I'm pretty hesitant to get any lubricant on or close to the filament. I oil my lead screws and inside of my bearings. Spray lubricant generally isn't recommended as it is hard to keep off of surfaces you don't want it on. Are you having problems with your extruder that makes you wan't to put some lubricant on it?