So my 318 has a driver side lifter tick

It's not bad unless it sits a few days and it froze up last night pretty cold. Tick goes away with just a few minutes of idling (at worst it's BARELY noticeable when I rev it) and once you drive it it goes away. Would a bit of Marvel Mystery in it before I change out the oil be good?

I'm a big believer in synth oil. I use Rotella T6 on all my rigs, all old, even motorcycles (it's certified) because of how it protects (and I've seen evidence at tear down). I usually top off with aternating quarts of dino and synth to save on the old leaky beasts. Even a can of STP now and then (in the summer). Will that help? She blows no smoke at all out the tail pipe and I don't wanna tear it down. I don't need it to do long or super hard miles, but I want her to run healthy as I can.

It also has a pump at the top of the motor I think is AC? That seems to be making some noise, I don't imagine that's good, and probably bad for mileage? It almost looks like it would be hard to delete from the system though because of the belts (1980 B350 Van).