I also had the rattle on start up. Spoke to the dealer they recommended extreme duty oil. (heavier) It help but if it sat for a few days still rattled on start up which is alarming to me. I bought and installed the Weller automatic cam chain tensioner and so far has been great. No rattle even after sitting for a week. As far as the install I ran motor to build up oil pressure. Turned it off. unscrewed the old tensioner ( stock one) then I installed screwed the new Weller one in. I did put the new tensioner in motor oil 1st and squeezed the plunger numerous times to prime the tensioner and push out any air so that on start up it would pressurize almost instantly. I didn’t do all the recommended timing procedures remove valve cover position valves etc. and it worked great. I got lazy and read that others had just screwed it in and it worked for them.