engine oil??

[SS Shaun]

Ok so when i rebuilt my motor i had a friend of mine tell me i should run 20w-50 in my 454. I have not had any issues as far as oil goes my pressure stays while nice and warm about 27psi at idle. I had good bearing clearance with no issues. I want to change the oil on the 454 this week since its been a few months i was thinking about going to 15w-40 since its getting cooler out now what do you guys think? Also should i add a bottle of zinc to my setup since i have a flat tappet cam?