My folks have a 1997 Tahoe, 5.7 v8, owned since 2002. Currently has 297,000 miles. Last 10 years or so it was retired to solely snow removal duty. Has had a steady diet of “whatever 5w30 is on sale” mostly synthetic blends, occasionally conventional or full synthetic. Most recently has gotten the “random leftovers” treatment.
I have a 2014 Silverado 1500 5.3 with 184,000. I have the full service history. Steady diet of AC Delco Dexos 0w20 done by the dealer until my ownership 3 years and 30,000 miles ago. Now it also gets what’s on sale, both 0w20 and 5w20. Will be switching to 5w30 when the stash of the 0w20 and 5w20 is gone