Oil Pressure Drop at Idle
That 20w-50 oil might have something to do with it too. Using high viscosity oil is old school. He might want to try a 10w-40 oil. For years now GM has been recommending 5-30w in all the newer engines. GM crate motors recommend 10w30 or 10w-40 oil. On a 454 I rebuilt with new rotating assembly, correct bearing clearances and a high volume oil pump my pressure was 80lbs. cold and 60lbs. hot with 20w50. I called my machinist and talk with him about it. He told me to drain it and use 10w40. He said they haven't used 20w50 in years. BTW after I changed to 10w-40 my cold pressure was 60 and hot pressure was 40-45. Another thing I tried using in my motorcycle was 20w50 synthetic. In the mornings with a outside temp of 40-45 and the motorcycle at operating temp. I was going to work and rounded a curve on a bridge at 45 mph. The oil light started flashing. I pulled to the side of the road after getting off the bridge. I cut it off and restarted, revved it a couple of times with no light. It did it again the next time I was riding. I bought it back home changed the oil to a 10w-40 synthetic and never had anymore problems. The motorcycle was new with less than 3000 mile on it.