Causes of High Pressure Reading:
Pressure remains high after cold start. Oil flows adequately into the pump, but does not flow through the oil galleries. Possible catastrophic failure. Shut down engine. Use oil with better low temperature properties (5W-30 or 0W-30).
Oil is thickened by soot load. Potential engine failure. Change oil and filter. Check injector performance. Avoid excessive idling.
Oil is thickened by oxidation. Potential engine failure. Change oil and filter.
Oil viscosity is too high. Oil flow is poor. Potential engine failure. Consult owners manual/oil supplier for correct viscosity grade. Change oil.
Filter blocked. By-pass valve allows unfiltered oil to circulate. Reduces engine life. Change filter and oil. Investigate cause of blockage.
Deposits in oil gallery system cause increased back pressure. Reduces engine life. Change oil and filter. Use higher quality oil.
Oil too cold. Potential engine failure. Check engine thermostat system. Check to ensure correct oil viscosity.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)