In your case that would not be the correct fill plug... On a '05 the fill plug is actually in the pan itself. That big circular depression in the pan that is right in front of the drain plug is your filler.This type of filler plug will make the job a little bit messier but what happens is the filler plug is recessed in the pan to hold back the fluid until it is at the correct level... Same filling procedures as pre '03 x5's apply though!