I was also wondering on whether a worn engine would do better with a higher weight rating, or is it more about the additives in a high mileage synthetic oil?
It depends on the problem you are trying to hide, but in my experience changing oils do nothing. Having kids that have bought cars with no oil pressure, running them out of oil, or burning oil there is really only one solution and that is fix the problem.
Put bearings in or rings in. Whatever it needs. We have tried to get around doing that probably most ways imaginable and it just doesn't work.
Thicker oils, maybe they coat better, stay in place better, maybe they don't get sucked past the rings as easily, but they also don't cool as well, or flow into places as well to protect the other parts that are still working correctly.
Maybe the high mile oils have some additives that help seals in some way, but in the end it is just a band aide not fixing anything just hiding it.
These are not old school V8 carbureted engines with big heavy cast iron heads and copper bearings. These are light cheap engines, with plastic guides and aluminum bearings.
Granted your 92 is a mix and will survive on just about any oil, your oil pressure gauge is not really a gauge. it is more of a switch, put a gauge in if you really want to know, but the only way to increase pressure is new rod and main bearings.