Drop the oil pan and check the condition of the rod and main bearings. It's not uncommon for a cold engine to have good oil pressure, and then it drops a lot once the oil and the parts warm up. If the crankshaft isn't worn excessively or out of round, changing the worn bearings will bring the pressure back up to normal. Anything over about 2 1/2 to 3 thousandths of clearance on any bearing is excessive. 1 1/2 thousandths is better. 10W-30 oil stays at the 10 weight thickness all the time- - - -it just lubricates like a 30 weight when it's hot. Switching to a physically thicker oil like a 20W-50 or a 15W40, or even straight 30 weight will help keep the pressure from dropping to dangerous levels until you get a more permanent fix done.
Jerry

Last edited by Hotrod Lincoln; 02/03/2010 3:10 AM.
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