My favorite has always been motorex 206. It feels like the balance of goes on thin & easy to work with & evaporates to the perfect tacky ness & still very easy to clean off with dish soap.
Its also very hard to come by now so I use powersave oil,also hard to come by at times & not tacky enough for me but cleans well.
I got some oil from TKO a while back that I used in between the others & that works well & is what I will probably stick with. Its in stock everytime I'm on his site for the other little cool things he comes up with.
I will tell you this much I'm done trying all the dirt bike oils. Over the years it feels like they have all gone too tacky(except the motorex) & while it may be good for my expensive ass 4 stroke its too much for my little motors.If its gonna be that hard to clean my filters I might as well just buy them by the truck load & not clean them.I should clarify my view on filters,I want them spotless,I replace the outers every time the car comes off the track & the inners every week some times every other week so I have alot of dirty outers to clean & cant afford a new filter every time.Most RC brand oils are for the most part WAY overpriced for me.