Mine regularly reads 3.5 bar at idle, 4.5- 5 under load at speed, and occasionally drops to 1.5 at idle after prolonged (3+hrs) use. Its read like this since I've had it over the last 15 months. Runs well, so could be a characteristic of my particular gauge. If your regular with oil changes and there's no discernable faults, I wouldn't worry too much. A marked change from the "norm" would worry me more.
