2003 XJ8 coupe 29,000 miles. I noticed that when I break the oil pressure gauge on the dashboard goes right down and a red light appears with the word Low Oil Pressure. After a few seconds, it then resumes to the normal middle position and the light goes off. I have also noticed a very slight noise coming from the engine when I put my foot on the acceleration peddle. It seems like the car is running at slightly higher revs. This error has taken place from cold and warm start. Can anyone tell me if this is something potentially expensive or a common fault on this model / make?