I started using DOT5 well over 25 years ago. Primarily to save the paint on my restorations. I always get the stuff all over everything. DOT 5 does not hurt the paint, and I have certainly got enough of it on the paint to know. I have never had any problems out of 5 and I use it in all my old Mopars. But if the problems with paint on the 3 and 4 isn't an issue for you, then there is no real reason to due the changeover, in my opinion.