I have a 2002 Ford F350 7.3 Powerstroke Diesel. I have tried several 15w40 diesel oils in my truck all with good results. I have been using Delo 15w40 for the past few years with good results. Honestly, if you stick with good diesel oils ( Rotella, Delo, Delvac, Valvoline Blue, Motorcraft and Castrol) you will be fine. Also, a good oil filter and proper change intervals are just as important.