Pellet lube yes or no?

It all depends, if your gun is not shooting to what you think it's accuracy level should be … it never hurts to try some lube to see if it improves. Sometimes it will aid in keeping the barrel clean longer between cleanings and cut down on leading. I have a Marmot Militia Hammer Forged barrel on an old Marauder that I use FP-10 on and it seems to help. You could also try One Shot Case Lube … a dry lube, but it is somewhat expensive.
 
25 years ago I started to lube my Field Target barrels with LW barrel and hammer forged BSA My fellow competitors were al using One Lube by Slick50.

Mine is aersol can and has many uses around the home. Tests have been done to see if long term exposure to this lube will harm seals. One Lube rated best. I use it on all PCP.It helps both accuracy and ease of seldom cleaning.

I shoot dry pellets in piston.
 
It depends a lot on the gun. My Rapid mk ll in .20 Cal was shooting the new jsb exact heavys 15.9 3/4" @ 75 yds After lubing pellets with 50/50 mix of wd-40 and marvel oil groups tightened up to 1/2" . Barrel very seldom need cleaning and a crown saver pull though will do the job. I'm pushing the 15.9 @ 910 and need a little protection from leading . Your milage may vary.
 
I don’t lube or clean the barrel of my 97k. Over 5000 pellets since it was last cleaned, pellet on pellet still if I do my part. If it’s not broke.....

This describes my Brocock Commander -- and I've found that shooting one type of pellet (in my case CPD) consistently makes everything quite predictable.

I think the pellet washing, lubing, and drying is as important as shooting only shiny lead pellets instead of the lead pellets that have oxidized and lost their luster -- and by imporant I mean not important at all :)
 
I will throw my 2 cents worth in. With a lot of magazines being self indexing, and somewhat closed up, I dont like using an oily or waxy product because of ending up having to clean the insides of the mags someday. But I do like to use a lube. I also like Hornady one shot case lube. It dries to a non sticky lube in seconds, and I have not found a barrel yet that shot different when using it. But they sure clean up easy. I just pour a small tin of pellets on a paper plate and make sure they are all laying on their sides. Then I spray them lightly ,then roll them around a little to get a different angle on them and spray them again. It sure has worked well for me .
 
I’ve recently cleaned a couple cans of Eun Jin 43gr pellets and lubed them with the same 15w40 full synthetic oil I use in the AV4500 compressor. 

Resulting groups at 70 yds through a Marauder are significantly improved. The first couple of magazines through the barrel were mixed results but continued to tighten up with more shots through the barrel. Group size (eight shots) has shrunk from 2.5 inches to about 1 inch. 

That’s shown me enough results to go ahead and clean and lube another dozen cans of the Eun Jin’s.