OP @wwillson has the same exact problem as I do - burn off in high EGR temps, if his testing proves that HPL 5w30 Dexos D is indeed helping with burn, then I am sure they will get a few more orders for 5w30 Dexos D. I have tried different 0w20 brands of Dexos D-approved. My observations are non-scientific but I do drive same routes again and again across the state weekly, AC Delco was burning off most, Mobil 1 was slightly less (folks on forums say that Mobil 1 makes AC Delco Dexos D oils but I do not know if true, bottles certainly look very similar). With AC Delco I am 1/2 full on probe shaded area in 4K miles, with Mobil 1 I am 2/3 full after 4K. Of course different weather, season, speed, so many factors that are different but same trips. I wonder if @wwillson will be able to notice the difference in burn off with HPL. Watching this thread.
Even if Mobil1 makes the oil for AC Delco that doesn't mean both sell the same oil. I'm sure they will blend your version of dexos D aswell, if you pay for it.