7MGE oil pressure problems

[I h8 Hondas]

Not sure what weight oil it has in it. I just got it a few weeks ago and the oil was near the full mark and looked pretty new when I pulled the dipstick so I didn't think anything of it until now. It's been on jackstands most of the time I've had it. It needed shocks, ball joints, front brake pads, and rotors and since I live on a farm I didn't have much time to work on it til this last weekend. The mechanic said he wasn't going to start it up again until it had new oil. We are planning to put Valvoline 10w-30 in it unless somebody tells me different by tomorrow morning.

Looking at that link the pressure seemed to be within spec. Any ideas as to why the pressure would just start dropping other than just rpm's decreasing? Speed limit was 35 where it started dropping so the revs were down but it never dropped that low at that speed before and I was going about the same speed in the same gear as before. It had been leaking a little bit out of the valve cover before but when we opened the hood but it didn't seem to have gotten any worse, and the oil was still well above the add mark.