I have theory about this. I have noticed a number of people who switch oils noticed lifter tick noises after the change. I suspect the oil change resulting in loosening some varnish or sludge that then lodged in the lifter area causing the lifters to stick, causing the ticking sound.
I would start out replacing some of the Mobil oil with a quart of Lucas and maybe a pint of MMO and just run it for a while. Mine has 248,000 miles on the odo, (not sure how much work has been done on the engine, as I bought it at 224,000 miles), but it developed a load tick/knock at around 230,000 miles. I changed the oil every 3,000 miles with MMO and Lucas as additives, and the last oil change I used Castrol Syntech (another long story of massive oil leaks), replaced the lost oil with Lucas, MMO, and some straight 50 WT Exxon dyno oil while replacing the oil filter adapter orings, and upgrading to the large oil filter. Long story short, the last 2 months of the summer here, the ticking/knocking is nearly gone, like 90% reduction in the sound level of the noise.
I think the Syntech completed what the MMO started cleanup wise of years of oil / engine abuse and finally unstuck everything. I still use Lucas and 20W50 oil, but I think the synthetic mix and MMO did a gentle cleaning of the engine with out overwhelming the oil filter or oil pump screen.
Some posted earlier this week taking the rapid approach with a quart of ATF for like 500 miles, then he drained and replaced the oil & filter and the very load tick was gone. It worked for him, but can be risky if there is a lot of sludge built up over the years in the engine from running dyno oils too long.
