Hi Dave Greetings & warm welcome to the forum. Re: how much oil to use in a D14 ?, there is an oil cup on top of the steam chest, unscrew the cap & top it off, make sure to put cap back on as this is a steam escape route if cap not screwed back on. fit. a drop of oil on all moving joints is sufficient. no oil is to ever be put inside the boiler.
Will it cause any harm or damage if oil is put into the boiler?