cyphen

I recently changed the oil in my r33 GTST to Penzoil Synthetic 15 - 30. I don't know what sort of oil was in there before but the 15 30w hangs around the 2 mark on the pressure guage at idle and rarely above 4 on freeway driving. The previous oil would idle round 4 and be around the 5 - 6 mark at 3000rpm. Some people have told me its bad to have low oil pressure but can't tell my why other than the obvious NO OIL!!