changing oil filters - Doc
When changing oil filters, the makers tell you to coat the rubber sealing ring with engine oil.

I still use the method that used to be recommended years ago which is to smear grease on the seal.
Does any one else still use this method and what is the purpose anyway?

changing oil filters - Sprice
Coating the seal makes it easier to remove the filter when the time comes. Grease or oil will do, but as new oil will be to hand during the change, it makes sense to use a little to coat the seal!
changing oil filters - defender
doc its only to let the rubber seal slip as it tightens so that it doesnt stretch the rubber then spring back a little as you let go.any lubricant does the job