Every once in awhile a dye kit will save your butt. Usually they aren't needed.................until you need it. I had one oil leak that turned out to be caused by a bad block casting (porosity) that almost killed a paycheck. I would have never found it without that UV dye. If you do use UV dye, get a little AA/AAA flashlight with a UV LED. It is a great timesaver and fits everywhere larger lights don't.