Wow,what a salesman.Is he going to void the warranty on the $30 chain if he finds oil on it?
Just do what you want;nothing has changed,oil is a lub.
I hate oiling chains-bicycle,mc etc because I am always fooling with them,and I absolutely hate getting that black grunge on my hands-pants-shirt,Really strange phobia for someone who likes to fool with bikes-cars-mc's.
I'm going to try something a bit different soon.I have a new SS chain.I plan to strip it of all oil and completelty clean the cassette.I'll then run it and see just how much wear I get on the chain-cassette etc.I probably should try one of the Teflon chains also.
Use what you like.It is a safe bet that the bike salesman isn't a lub engineer.Luck,Charlie