the only reason that the auto tensioner will fail is of bein too old.... a new mitsubishi tensioner with factory belt setup has gotta be the best way in my book... yea you have to pu it in the vice when you change the belt.... but as long as you keep the pin, its not a big deal, i dont have a vice in my garage yet... but i always figure a way to get it shoved back in... from wat i know the factory tensioner on my vr4 before i bought it helpd up over 100k miles before the belt broke and dinged the pistons.... i bought it thousands of miles after that and dont even know if they put a new tensioner on it then, ofcoarse i have since then but the auto tensior is a way better way i think... rpms cant do anything to the tensioner, just the pulley the tensioner pushes on