Even a 20w50 should lubricate the top end as well on a cold start, as the Sae 20 that the shop manual mentions.
The heavier multi-grade oils (15w40, 20w50) do offer some piece of mind in that they are “allowed to” (by modern standards) have a higher level of ZDDP than those in the 30 range. You are more likely to get a decent ZDDP level with those heavier grades, but unless the manufacturer will share the level or you submit a sample for analysis, you can’t just assume as much. Some diesel oils have had their zinc levels greatly reduced and the high calcium detergent in them further reduced the effectiveness of whatever is there.
For some heavy “reading” on the subject, go check out some of of Lake Speed Jr’s videos under the “SpeeDiagnostix” channel. You can geek out for a few hours if you like.
My oversimplified take on all this: Most of the engines represented on this site are some degree of worn out. 15w40/ 20w50 probably ain’t a bad idea. Excess viscosity/pressure DOES rob horsepower, but it’s not like many of us are trying to shave off tenths at the drag strip.
