I've noticed that when it's cold outside -10c or 14f my car will sometimes show no oil pressure on the first start. I shut it off right away and wait for a minute and try again and it usually has pressure on the second try. Once the car is started and warm the oil pressure is fine. When the temp is warmer and starting it the first time pressure is good. I changed the oil and filter 2 weeks ago with synthetic 5-20.(I've always used synthetic). I'm thinking it might be the pressure switch. Anyone have this happen before?