Mazda Repair: 1992 miata oil pressure, oil pressure gauge, true sports car

Question
what is normal oil pressure when idleing and going about 40mph+
i have 30 idleing and about 60 65 at 40mph+

Answer
On 1990 thru 1994 Miatas oil pressure is calculated instantaneously and is reflected on the gauge as such.  Pressure varies by oil weight, temperature and engine RPM.  There is no base line pressure to give you due to these variables.  A hot Miatas pressure can be as low as 10-15 psi at idle while a cold Miata can generate over 90 psi at RPM.  Hot oil is thinner and moves more readily whereas cold oil is thicker and requires more pressure for it to flow through oil galleys.

Newer Miatas came equipped with variable read sensors which take periodic reading not instantaneous readings.  (ie: the oil pressure gauge remains more stable, not a trait of a true sports car)  

Rules of oil pressure;
A zero PSI reading at idle is bad.
A reading above 90 PSI is bad and works to test the seals.

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