Ive owned four 5.7s starting in 2005.
Changed all of them with 5w20 full synthetic, no real allegiance to a brand, but always a major brand (Mobil1, Valvoline, etc); typically 5k - 7k miles between changes .
2005 had 250k , burned no oil, died when it hit a tree
2006 had 240k, would use 1/2 qt over 5k miles after about 225k.
2013, traded in with 225k, burned no oil.
None of these ever had a valve cover off. I purchased the 06 and 13 new. The 2005 I purchased with 100k on it.
The 4th is a 2021 with 35k on it. So far, so good.