Ideas welcome.. ;-) UOAs are from different cars but I'm afraid that problem is the same - no low saps oil (only 5W-30 C2 or C3 allowed by Subaru) to survive 15kkm recommended by Subaru.
Cars have open DPF - not regenerated by fuel injection.

This one is currently tested on the same M1 ESP but with BG112 (DOC) additive (added after few days to oil). 15kkm planned - we'll see if BG112 helps.

The second one (the Motul used was 8100 Eco-clean C2 5W-30) has been cleaned/flushed and filled with Amsoil AFL 5W-40 C3 for 7500km test - owner probably will change oil every 7500km.

Toyota Avensis 1.8 Valvematic MY14 Specol Gold 5W-30
Alfa Romeo Giulietta 1.4 MultiAir Turbo MY10 Meguin 0W-40 Driver, Archoil AR9200