I think 5-W20 is way too thin an oil for this engine. I think the ticking is the result of such thin oil as it does not adequately pressurize the oil carriage system AND it doesn't provide the buffer necessary to protect the internals. Now I have nothing to back this up except to say my 5.7L GM motor makes a helluva tappet sound (generic so many of them do it) and when I increase the viscosity by 10 it is noticeably quieter). Thats my story and I'm sticking to it. Too thin an oil (by 50%) may be most of the ticking sound.