Mike---A drop in oil pressure as you describe is usually caused by
what's referred to as a cavitation in the oil supply, which is a fancy
description for an air pocket. I have found this occasionally when
accelerating quickly before the engine oil has had a chance to thin.
Also when going up a hill under the same conditions. What seems to
happen is a lot of the oil hasn't had a chance to return to the sump,
and the pump can draw in air, which registers as a temporary drop in
pressure. In most cases this will not occur if the oil level is at, or
slightly above the Full mark on the dip stick.
Dick Taylor
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