Cummins Onan Generator oil
After countless hours of searching, I could not find the the oil specs recommended for the rv generator. I finally broke down and went to my local Cummins center, and bought the factory Onamax 15w-40...
Forum Discussion
As previously mentioned 15W-40 weight oil is typically diesel engine lubricating oil and will meet the viscosity recommendations for almost any operating temperatures where you normally run your gas engine Onan genny. Although they are listed on the Onamax label, a lot of the specs that the OP listed are obsolete and have been superseded by more recent API specs/certifications which are generally backwards compatible. Onan's marketing and advertising department is just trying to confuse you and motivate you to spend more money on THEIR product. API CJ-4 and SM specs are current. Chevron DELO 400LE, Mobil Delvac, and Shell Rotella will all meet the specs Onan requires and typically cost about $12 to $14 for a 4 quart bottle. (less when on sale) Today I just went into Camping World and they want $11.95 for a quart Onamax genny 15W-40 oil. Aaaaahhh, no thank you. The above referenced products are widely available (Walmart, Costco, Kragen, Napa, Autozone, Oreilys, etc.) and, IMO the best deals in any town.
Onan manufacturers generators, they do not manufacture/blend oil. They simply buy bulk oil made by others that meets their specifacitions, repackage it in their proprietary containers and +-double/triple the price. If you prefer to buy Onamax oil or other $$$$$$$$ designer/boutique oils (synthetic) suit yourself.
Chum lee
Onan manufacturers generators, they do not manufacture/blend oil. They simply buy bulk oil made by others that meets their specifacitions, repackage it in their proprietary containers and +-double/triple the price. If you prefer to buy Onamax oil or other $$$$$$$$ designer/boutique oils (synthetic) suit yourself.
Chum lee
