Got a question that might seem a little dumb (and why it did it was kinda my own fault )but before I do anything crazy power wise to my truck (Cam, gears heads) I have an issue with my truck that started after I ran the crap out of it one day about two months ago. Left the oil cap off on a rainy day (don't know if maybe that helped it out but its always a possibility) after topping off the oil and went to town and back flat footing it and having a grand old time here and there but when I got home and checked my oil pressure it had shot down from 25 where it used to always sit down to 20 psi, now this of course this scared the hell out of me but I keep on driving it cause it was my main DD at the time, then a few days later I did the same thing, flat footing it only passing some slowpoke and this time it went down to 15 psi, Now its been about two months since it went down and up until I fixed my oil leak I had added about a quart of 10w-40 semi-synthetic motor oil and even in this heat and allot of hard runs its still holding the same psi at idle just fine and builds pressure good still. Its just well lower than it once was and if I wasn't gonna mod this engine I'd just leave it alone and not worry with it. However that's not the case and the last thing I want is to lose oil pressure and do damage to anything new I put in there let alone whats still in great shape, parts ain't cheap you know. I'll get some exact numbers in the morning on the colds and hots at certain rpm but if my mind is not mistaken when the engine is hot at about 4000 rpm its holding 50 psi. One other thing to note is that as soon as I raise the rpm just a little the oil pressure shoots up just fine and it doesn't flutter around at idle. What I'm asking is what all I should check out on this engine to help get the pressure back up to a safer area or if where its at at this current moment is perfectly fine for me and I'm only over-thinking this. Thanks in advance and sorry if this post is kinda jumbled up on the information.

 

I would start with a fresh oil and filter change before worrying about anything.

General guideline for older Ford engines: 10 PSI per 1000 RPM

So 50 PSI @ 4K RPM sounds fine.

 

Thats what my old man was telling me to go by as well. As for the oil change that was done a month ago with supertech 5-30 motor oil and I added a quart of 10-40 semi synthetic oil in because I had a slow oil leak that I just fixed a week ago. cold psi at idle is 35 psi and at 3000 rpm cold I had 55 psi.