Break-in
Ram's owner's manuals for the 6.7 say no special break-in period is required, and add a few habits for the early miles:
- Warm up before loading the engine heavily.
- Avoid long idling.
- Use the right gear so the engine does not lug.
- Vary throttle and speed when towing.
- Watch gauges and check fluids often.
The manuals say the engine keeps seating in through the first several thousand miles of loaded use. A Cummins statement printed in a motorhome chassis manual says Cummins engines are run on a dyno before delivery and that special break-in oils are not recommended.
Storage
- Do scheduled maintenance, or at least change oil, before storage.
- Fill the tank with fresh fuel from a busy station. Cummins advises against biodiesel blends for storage.
- Check coolant freeze protection.
- Tighten the DEF cap.
- If possible, run the engine to full temperature at intervals, per the Cummins guide.
- Maintain or disconnect batteries.
Generators
Cummins Onan says to exercise the generator regularly under load, and its storage steps include disconnecting the battery and protecting the exhaust outlet from pests.
Where this comes from
- Ram 2022 2500/3500 owner's manual: engine break-in recommendations (Mopar)
- Ram 2017 chassis cab owner's manual: diesel engine break-in (Mopar)
- Tiffin Motorhomes: 2020 bus chassis manual (Cummins engine section, PDF)
- Cummins: Motorhome quick reference guide, L9 / ISL (PDF)
- Cummins: Diesel RV engine operation and maintenance presentation (PDF)
- Cummins Onan: RV generator operator manual (PDF)
- Tiffin Owner Hub: Cummins Onan generator FAQs
Last reviewed 2026-10-19. General information only: your owner's manual and service information come first.