Generally, you should see:
* At idle (warm engine): Between 10 and 20 PSI. Some slight variation below 10 PSI at idle is acceptable for a well-worn engine, but consistently low pressure is a concern.
* At operating temperature and higher RPMs (e.g., 2000-2500 RPM): 30-40 PSI is typical. Again, some slight variation is normal.
Crucially: Don't focus on a single number. Observe the *trend* of the oil pressure gauge. A consistent reading within the above ranges while the engine is running normally is good. A sudden drop in pressure, or fluctuating pressure, indicates a problem.
If you're concerned: Consult your owner's manual for the specific recommendations for your year and model of vehicle. It's the best source of information for your specific engine. Low oil pressure can lead to serious engine damage, so it's important to address any concerns promptly.
