GMC 1999 Sierra 1500 Pickup Owner's Manual page 157

Oil Pressure Gage
Standard Cluster, Gas Standard Cluster, Diesel
60
K2335
Tachometer Cluster, Gas Tachometer Cluster, Diesel
The oil pressure gage shows the engine oil pressure in psi (pounds per
square inch) when the engine is running. Canadian vehicles indicate pressure
in kPa (kilopascals). Oil pressure may vary with engine speed, outside
temperature and oil viscosity, but readings above the low pressure zone
indicate the normal operating range.
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