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Handbook / Other owners / RV and motorhome

Chapter 2 Other Cummins owners

Owning a Cummins-powered motorhome

Diesel pushers often run the Cummins ISB (now B6.7) or ISL (now L9). They rack up fewer miles than trucks but sit for long stretches, and that changes the maintenance story.

Late-1990s Class A motorhome parked on a city street
Class A motorhomes may sit for months between trips. Photo: Oleg Yunakov, CC BY-SA 4.0 (resized), via Wikimedia Commons.

Start with the Cummins motorhome guides

Cummins publishes motorhome quick reference guides for the B6.7/ISB and L9/ISL with the maintenance schedule laid out by time and miles. Keep a copy with the coach, and follow whichever interval comes first.

Rear radiator and cooling

Rear-engine coaches pull air through radiators and charge air coolers that collect road dirt and debris. Owner magazines and Cummins both treat cleaning them as routine, especially before summer trips. See coolant.

The generator counts too

Many coaches also carry a Cummins Onan generator. Onan says to exercise it regularly under load, and to follow its own storage steps when the coach is laid up. See storage.

Buying a used coach

Ask for engine and generator records, check the generator hours, and have the chassis inspected separately from the house systems. See the RV section of the used checklist.

Questions

Which Cummins engines are in diesel pushers?

Commonly the ISB / B6.7 and the ISL / L9, depending on coach size and year. Cummins publishes motorhome guides for both.

Where this comes from

Last reviewed 2026-10-19. General information only: your owner's manual and service information come first.