When does it read 50psi, idle, at speed, fully warm. What model car ?
As stated oil pressure is a constanly adjusting measurement that is affected by oil viscosity, engine temp & engine speed.
A simple baseline for minimums would be 15lbs at hot idle & 40lbs @ 3,000 rpms (hot). No reason to panic with numbers under this because more than enough oil get to critical parts even with these readings. It just means a rebuild is in your future. The rocker arms & shaft are the parts that would suffer the most because chances are that most of the oil is being dumped back into the oil pan before it makes it up to the top.
Depending on the motor the most likely places that cause this are the main (crank) bearings & cam bores. Increasing oil viscosity may reflect a higher oil pressure reading but may not necessarily pump more oil to the rockers. In either case 20-50w oil should be used for summer driving.