One was a company car. Also had a friends car do the same while I was in it. All were Australian made, all had idiot lights, all failed in the same way, sudden loss of oil through the plastic body of the switch, (and the light did NOT come on).
So far: A 79 XC Falcon (Like the Mad Max car, only 4 door) 4.1L 6. An 80 HZ Kingswood (kinda like a Chevy Malibu) 3.3L 6 A 78 Mitsubishi Sigma 2L 6 A 88 XF Falcon Panel Van. 4.1L 6
I suspect all the oil pressure switches were made in the same factory, and were defective. All cars were over 5Y old. Can't see it being anything I was doing wrong.