Re: low oil presure
The stock gauge may or may not be accurate. However I suspect it is rather accurate in relative terms. Meaning, if his oil pressure was high (normal?) in the past and he’s seeing it low now it probably -is- low. At least a lot lower than it was.
That being said true low oil pressure means something is wrong. It can be any number of things but some that come to mind are: Bearings (rods and mains and cam), clogged oil filter, low oil level. If this a sudden occurrence then a bad sender would be the first thing I’d check.
Regardless, installing a real gauge and measuring actual oil pressure would a logical first step.
Don