Ouch.I would refrain from any greasing, oil, WD40 or other lubricants My 24-105 never did this, my 70-300 is a non-L and has no weather sealing.Sorry that I have no lens to compare :-( but I would hope to get an answer from one of those lens rental guys, as they have a large amount of such lenses and maybe could underpin or disagree to Canon's opinion that this is normal...And I totally agree: n