Does anyone know what the oil pressure should be like if it is measured from the plug on the front of the engine? I checked mine and was surprised to see that there was a pressure drop of about 1.50 KPa caused by the combined resistance of the oil filter and the oil cooler. This seemed a lot. Unless I have mucked up the units this means that if my minimum oil pressure was 2.0KPa (which is were the yellow strip starts on the gauge) It is usually about 3.0KPa. Then the gallery/bearing pressure would be rather low. (0.5KPa)
This could be correct. There can be significant oil pressure drop across the oil cooler and oil filter when the oil is cold. This is also when the oil pump/engine develops the highest oil pressure, therefore even with this pressure drop there is still more than enough oil pressure in the gallery. When the oil is hot and the pressure is lower the pressure drop across the oil cooler and filter is also significantly reduced. The oil pressure limits for the engine were developed taking this into account (assuming standard jabiru oil cooler). This is also why multi-grade oil is good in cold seasons, e.g. Shell 15W-50.
