Generator opil change

oil filter cross over to a napa number I use 15-40 synthetic oil in my 5.5

Thank you everyone. This will save me both cash and the effort to obtain Onan brand.

Rotella

I use this in my Onan 5500, have been for the past 10 years in both generators. (from my previous Class C) . Hummin along. I also replace the fuel filter ever other year. I drop the oil every 50 hours and the filter at 100. (every other change) I was told it is very good oil, has lots of detergents in it to keep the engine running clean. I also use it in all my lawnmowers, etc at home too.

maybe a little overkill..:C but i change m/h fluids every spring no matter what the mileage is and change the genny oil and filter every 100 hrs. and i use Royal-Purple 15w-40 synthetic.

IMHO, if ONAN oil and filter have anything to do with your 16 year old generator "humming along".....stay with it.

FWIW, my gasser GENERAC uses "any quality brand" 10-30 (as stated in the owners manual). While GENERAC does not offer their brand oil, they do offer their brand oil filter. For 9 bucks.
NAPA has the same thing for 4 bucks...and I also use NAPA 10-30 in the motorhome and generator...along with my car and pickup truck.

Like you, my 12 year old genny keeps "humming along" too. The way I see it, as long as your oil meets the ONAN "requirement" API standard, the brand really doesn't matter.

My genny oil and filter get changed once a year,in the spring, along with the motorhome motor oil change.

Rotella. Delvac. The premium multi-vis oils blended for 200-500 hour use in water cooled diesels are up to the task of lubricating an air cooled engine on its shorter change interval. Onan likely does not blend its own branded lubricants, they would be buying from one of the handful of majors in the lubricants business, and at 15W40 the specs are probably pretty close to those for diesel blends.