Oil pressure still fluctuating, amything i can do about it?

Still the 1988 Ford F150, oil pressure was good on the stock dash gauge until the weather started getting hot and humid, now it drops scary low and then slowly comes back up and then drops again, anything i can do about that? hoping my engine isn't just wore out beyond any help
Update: 153000 miles but it had 128000 of those before I got it so i have no idea how it was treated before then but I do regular maintenance on everything like it's supposed to be done
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