* Engine condition: A well-maintained engine with new bearings will likely have higher oil pressure than one with worn components.
* Oil viscosity: The weight of the oil (e.g., 10W-30, 20W-50) significantly impacts pressure. Thicker oil at lower temperatures will give higher pressure.
* Oil pump condition: A worn oil pump will deliver lower pressure.
* Engine temperature: Oil pressure generally drops as the engine warms up.
However, a generally accepted range at idle for a warmed-up Ford 300 (after operating temperature is reached) is between 10 and 20 PSI. Anything significantly below 10 PSI warrants investigation. Extremely high pressure could indicate a problem as well, though less common.
Crucially: You should consult your owner's manual for the specific oil pressure specifications for your particular 1975 Ford 300 engine. The manual will provide the most accurate and relevant information. If you don't have the manual, you can often find a digital copy online.
Always check your oil pressure when the engine is at normal operating temperature. Cold oil will give a higher reading.
