The 15 PSI ..... is that at idle? What do you have at cruise? An old rule of thumb is 10 PSI per 1000 RPM.....
I've seen small blocks with very liberal bearing clearance experience "low
oil pressure" but stay together for years without a problem. If you can hold something around 35 PSI under normal driving conditions, I wouldn't rip and tear things apart unless you notice other symptoms of low
oil pressure that could signal a problem.