You to him...Yep.…
About 15 years ago, I had a mechanic at the Navy Exchange try and stop me from buying 0W30 Castrol (much loved on BITOG) on clearance.
“That zero weight won’t give you enough oil pressure on start up. It’s too thin. You need a 10W30.”
He was honestly trying to be helpful. And we talked for a bit, but he stuck to that point of: it is too thin on start up. I thanked him, moved to another row in the oil aisle.
And when he went back out to the service bay, grabbed two cases of that Castrol 0W30 that was on clearance.