My mother-in-law’s 94 Chevrolet pick up had a startup rattle as well. There was an AC Delco filter on it and the oil was full showing on the dipstick. I put Valvoline MaxLife and a micro guard on it and the rattle immediately disappeared, but this was about five years ago as well so take that for what it’s worth I reckon.My friend pulled one off his daughters Elantra that had a terrible startup rattle and sound he never opened up the can but we suspected it to be a damaged ADBV or torn media. Installed a Super Tech and problem was gone. And I wanted to like those Microgards I am glad I never gave one a try, one would be too many to risk it.