In 1995 when my PSD was new, some oils would start foaming very bad at roughly 2300 miles and the HEUI injectors would not operate correctly. The engine would seem like it was missing, even though it was a diesel. The only solution was to add the anti-foaming agent from Navistar or change the oil. When CI oils came out it seems this problem was eliminated and I have not seen or heard of any need for using the anti-foaming additives.
To be fair the 15W40 oils that did not cause problems were Delo 400, Delvac 1300S, Schaeffers, Motorcraft, Delvac 5W40 and all synthetic 15W40 oils. There were others, but these are the ones I know personally that cured the problems and allowed 5K oil changes on any PSD that had problems in that era.