Delo replaced the zinc with moly.
DELO 15W-40 has a lot less moly than it used to. I do oil analysis on my F250 on occasion and it went from 95-96 ppm back in 2017 to 2 ppm on my latest change (I can't believe the moly suddenly got "used up").
Zinc and phosphorus were both cut by about 20% back in 2018, IIRC with the introduction of the CK4 spec.
But it's still OK. My diesel hasn't exploded yet. I think 15W-40 is a bit thick overall for a stovebolt. Chevron (DELO) also has single viscosity oils as well as 10W-30 multi-vis, but the 10W-30 is a bit harder to find.
