Boarder Line Low Oil Pressure

I have a 325,000 mile 273, rebuilt 175,000 miles ago.

With 10w30 wt the idiot light would come on at hot idle. Sender was new at the time.

I went to 10w40 wt and no more oil light

No actual oil gauge so I don't know what it is running.

I will tell you that 10w40 is like cold syrup in 30 deg or colder weather