Good morning everyone. I have a 1996 k1500 5.7L with approximately 355,000 miles on the original motor (See attached picture). This was my grandfather's truck that I have been restoring since he passed away. Once I got it running again, I noticed that the oil pressure was low, about 20 psi when driving and 10 psi at idle. The truck has traditionally seen Castrol GTX High Mileage 10w-30 every 5,000 miles with an ACDelco PF52 oil filter. At the last oil change, I used 2.5 quarts of oil along with 2 quarts of Lucas Oil Stabilizer (4.5 quart overall capacity) in an attempt to raise my oil pressure (don't attack me, that was before I found this website and learned that Lucas is the devil's nectar). Overall, the oil pressure was raised and the truck has been driving good ever since, although the oil pressure is still slightly low, about 32 psi when driving and 18 psi at idle. Well it is nearing my next oil change and I am looking for recommendations. My current plan is to do a Liqui-Moly 2037 engine flush, and then bump my oil up to Castrol GTX High Mileage 20w-50. I was thinking possibly add in some MMO as well? I live in south Georgia so it never gets super cold here. I would love to hear your thoughts and any help that you may be able to give will be greatly appreciated! I hope everyone has a Merry Christmas!