I have an 01 TJ with 2.5 and 5-speed with 136000 miles. After engine has been run hard, and shut off, and restarted within 5, or 10 minutes, sometimes oil pressure is slow to pick up, and causes the check gauges light and chime to come on. It will always pick up, but it may take a few seconds, before it does. I am using Castrol high mileage 10W-30 oil, and Fram TG 16 oil filter. Most of time it picks pressure right away, and does not do this during cold weather. I have changed sending unit, but did not cure this. Could this be an oil pump relief valve, or an oil pump problem? It carries 40# oil pressure normally.