I just got my truck about two months ago. I noticed when the weather started to get colder that the oil pressure runs really high. It runs between 70 and 80 psi when i first start it and until the engine warms up to operating temperature. When it gets to operating temperature it runs just above 40 Psi. It is a 1999 chevy 1500 old body style with the 5.7 in it. I have not had a chance to change the oil it it yet so i am not sure the viscosity of the oil in it. I am going to change the oil next week and put 5w30 in it to see if that makes a difference. I was thinking maybe they were running a heavier oil in it and that is why the oil pressure goes down when it warms up. Does anyone have any other ideas or know of any issues this model may have had with oil pressure? Any advice would be great.