Do you top off at 25psi or does your oil pressure increase with rpm? For example, does your pressure increase to 35psi @ 3500rpm? 45psi @ 4500rpm? If not, you have excessive bearing clearance problems, a worn out pump with excessive clearances or a blocked pump pickup (pickup too close to bottom of pan or clogged with silicone, old gasket material, etc.) All this assume that your oil pressure gauge reads true.
Chuck is right on regarding volume vs. pressure. Excellent explanation! :thumbup: