If it was important DJI would tell you ... and they don't.
Lots of people want to feel they are doing "something" but it's not necessarily helping at all.
I'm with you Meta4 - here is my 2 cents worth...........
The bearings in the Phantoms are "ZZ" type - that double "Z" indicates double shielded (shield on both sides). A sealed bearing is designated with "RS or 2RS" (single or double rubber seal).
IMO only. I am doubtful they would have a double seal on these bearings turning at the rpm they do - rs bearings would create far too much heat (shielded bearings provide 2 essential outcomes - 1 being the release of heat from the bearing and lubricant and the other to prevent loss of lubricant - somewhat). I had one guy tell me Phantom bearings have nylon races (that would explain somewhat as to self lubrication) - I for one am very doubtful they have nylon races however.
When someone posts there motors were noisy or felt rough turning by hand and that oil quieted them down or made them smoother - they are somewhat correct. However, don't be fooled by results since once you hear or feel a bearing, generally speaking it is a little too late and the damage has been done - oiling would then be a temporary fix only. Considering the cost involved I would say it is best to replace after hearing any noise emitting from them and especially so if the motors feel a little rough or have slight tight spots when rotated by hand.
I have never seen anything from DJI with regard to lubrication of the motor bearings - I have been flying both the P3A and P4 for a couple of years now without ever lubricating. My P3A does have one motor that feels a little rougher than the other 3 and will replace the bearing rather than get into oiling. Since one feels just a little rough I plan on replacing bearings on all 4 motors with ceramic type. Ceramic bearings are lighter, smoother contact running (especially for high speed) and the L10 (life) is much longer.
It's a matter of choice I suppose when it comes to oiling - I firmly believe once you begin oiling you will have to continue oiling. Lubricants are all different - start adding the incorrect oil to these bearings and you may be introducing a mismatch relative to the make up of the original lubricant. Detergent properties of one lubricant Vs another may cause a "washout" of the other lubricant - hence requiring the oiling process to be continued fairly regular. Constant and over oiling can produce issues relative to dirt cling and increased temperatures also.
Speaking of dirt clinging - the props do a sufficient job of keeping airborne contaminants away from the motors anyway without having to use compressed air to clean them. If you start using compressed air to blow contaminants off the motors due to oil reside - there remains a slight chance you could blow some crap into the bearing also.
Until the OEM tells me differently - I will continue to fly as is. Of course, I do check by hand turning motors prior to flight and monitoring temps after flight (trending) each and every time in order to have good relative information regarding the rolling elements for the motor and to have a safe bird in the sky.
