Just wanted some feed back with out starting a heated debate over Delo 15w40 vs Rotella 15w40. I have a 2002 F350 7.3 Powerstroke Diesel. In the past I have used Rotella 15w40 with no complaints but started using Delo 15w40 about a year ago mainly because Costco has a decent sale 6-1 gallon jugs per case for $51.00. I purchased several cases feeling comfortable with choosing Delo. Does either oil out perform the other