Use the specified oil
Your owner's manual or Cummins guide names the oil specification and viscosity for your engine and climate. Newer emissions engines need oil that meets the newer specification.
Interval
Additives
A Cummins statement printed in a motorhome chassis manual says Cummins does not recommend aftermarket oil additives. Use the oil the manual specifies.
Between changes
- Check the level on level ground, engine off, after it drains back.
- A rising level or fuel smell is worth a diesel tech's look.
- Record each change in your logbook.
Where this comes from
- Cummins: Motorhome quick reference guide, B6.7 / ISB (PDF)
- Cummins: X15 quick reference guide (PDF)
- Ram 2022 2500/3500 owner's manual: engine break-in recommendations (Mopar)
- Tiffin Motorhomes: 2020 bus chassis manual (Cummins engine section, PDF)
Last reviewed 2026-10-19. General information only: your owner's manual and service information come first.