According to fords own workshop manuals minimum oil pressure at 850 rpm should be 1.8 bar or 27 psi, and at 2000 rpm should be 2.4 bar or 37 psi, From cold my own car shows around 80 psi on start up , dropping back to 50 psi when she's warmed up, idle pressure though is rather low at about 20 psi but this is probably due to the cars age and the fact that it has 130,000 miles under its tyres, its worth mentioning though that aftermarket gauges can be notoriously unreliable , especially if its accurate figures your after