Cummins, who is affiliated with Valvoline, does not recommend that type of interval even on their 15L ISX with a 10 gallon sump. But Detroit Diesel does have a base 50K OCI recommendation for their DD15 engines in OTR trucks.
Wow, I am trying to visualize that one... 12 and 18 gallons? I have owned a couple of Cummins, a N-14 and a ISX, and neither held that much. Same for 3406E and C-15 Cats. All of them got 10 gallons on an oil change. Oh, read further.. must be one of those Gulf Coast bypass filters. Those things alone take up to 3 gallons just by themselves. Thankfully the Detroit I have now only takes 10 gallons, even with a bypass filter unit.