Onan BFA Oil - Why not 20W-50?
Note: Our typical camping climate range runs from 10F to 115F (if we go to Redding, CA in the summer... otherwise up to about 105 in Southern Oregon.) Clearly Onan/Cummins have updated their recom...
Forum Discussion
KendallP wrote:
With all the viscosity index improvers needed to meet that wide spread in a conventional oil, you're not at all concerned about viscosity breakdown?
That is exactly why Onan didn't want multi-viscosity oil in their engines. Air cooled engines run hot enough to breakdown the VIs.
10W30 Non-Synthetic oil requires aprox. 11 percent VI. 10W40 requires 17+ percent VI. VI is not abrasive no is it a lubricant.
Many years ago, GM would cancel the warranty if they found 10W40 in the engine.
Some 10W30 synthetics do not require VI. So it should not be a problem in air cooled engines. Most 10W40 synthetics do require a small amount of VI.
I am privileged to have a petroleum engineer as a friend. The above info. comes from his desk.
Richard
