Checked the oil again and it is fine. I did notice today that while the car is cool, it doesn't make the sound. Once up to operating temp (about 2 or 3 miles) it starts ticking. Ticking is loudest at 1,500 and 2,500 RPM. Can't hear it at all when at idle.

 

oil pressure is not enough when engine warms up.
Oil grade Xw-30 becomes too thin when engine temp is around 100 deg C or 210 F.

Now I'm going to switch to 0w-40 .

 

I checked the FSM and ticking/clicking that starts after the engine is warm can be tappet noise from a valve that needs to be adjusted.

This might be my little project for the weekend. I'll check with the local Nissan dealer and my trusted mechanic to see what they would charge.

I have nearly 100,000 miles so I'll probably take the opportunity to change the plugs while I'm in there.

 

I should clarify that I'll check clearance. If it needs the valves adjusted, I'm not diving into that right now.