Manufacturers recommendations usually are very conservative. So if something goes wrong in the engine they have an out if you didn't change the oil regularly enough. Manufacturers do not want any come back during the warranty period.

My old Bedford 330 gets an oil and filter change every year. That's it! Even though Bedford recommend 100hrs like Cummins.

But consider this. My Bedford came off the assembly line in 1976. Has oil technology changed since then? It sure has. So why haven't the change recommendations changed to reflect this?

For sure, if you are working your engine really hard (like most commercial applications) likely you will want to follow the recommendations.

But if you are a gentle driver, know how to use the gears etc , for just normal RVing , you can spin that 100hrs out 2x or even 3.