Hello again.
I have a 97 Chevy astro with 245k miles on it. While driving it, the oil pressure goes up to 3/4 of the way up or around 60 at constant speeds. Then at stops or idle it drops to the halfway point or 40. After driving 20 mins or so it will drop to 20 while stopped or idling. Engine sounds solid with no detectable problems. My mechanic friend told me switching to a heavier oil would help this a little, suggesting 20W50 during the summer and 10W40 during winter. Would this be accurate?