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Rockyroad · 11-10-2014, 10:51 PM

Hi Folks
My 1996 Class C has an Onan Emerald 4000 watt generator of the gasoline BGE series. I have the manual and I have checked on the unit itself, but I can not seem to find the recommended weight oil. Can someone give me advise on what Oil I should use. I live in SoCal and expect to use the unit in temps from say 40 degrees to 100. When on the road in the summer I use the Genset and the roof AC on most of the driving and put lots of hours in at temps in the 100 degree mark.

Thanks
James

Grandpere · 11-11-2014, 12:06 AM

Most generators use a straight 30 or 40 weight oil, but that is getting to hard to find. I use Castrol 20w-50 oil in my generator. It acts like a 20 weight oil in the winter and a 50 weight in the summer. I like the fact that it has a higher viscosity to help the engine wear. Also I add SFR 100's oil additive to also help with the wear as it is a great friction reducer and very tenacious in holding a film against the moving parts. Here is a link to SFR 100: https://sfrcorp.com/product/sfr-100-...oil-fortifier/

Hope this helps.

Mr_D · 11-11-2014, 12:36 AM

Maybe this is the owners manual: http://www.cumminsonan.com/www/pdf/manuals/965-0528.pdf

94-Newmar · 11-11-2014, 03:54 AM

Rockyroad, here is the owners manual direct from Onan/Cummins:
http://www.cumminsonan.com/www/pdf/manuals/965-0128.pdf

Recommended oil weight is based upon the ambient temps you will be running in most of the time. For most of us, the 15w-40 is sufficient. Onan has their own recommended oil, Onamax but it is difficult to obtain. An alternative is Shell Rotella 15w-40 which is widely available and what I use when Onamax is not available.

Should you be unable to download the manual, here is a screenshot of the relative page from the owners manual:

Rockyroad · 11-11-2014, 10:45 AM

Thanks for the info folks! It seems like the Straight 30W or the 15-40W would do the trick... Although I could also see a 20-50W may work will for me too. Hmmmm.

Dutch Star Don · 11-11-2014, 11:53 AM

"Rockyroad"....The Rotella 15-40 is available at Walmart in 2.5 gallon, 1 gallon and quart bottles. It's a quality oil and will serve you well as a generator oil. I know a lot of people use either Rotella or Chevron Delo in their DP's and put the same oil, either the Chevron or Rotella in their diesel generators.

The most important thing, since it's a small oil pan, is to just change it often. I change my generator oil once a year.