[Rich Biebel]

Onamax is the oil they sell for every machine they build

It's 15-40 which is/was commonly used in Diesel's for years.

I stopped buying it from Onan and have been using 15-40 Delvac. That is what our bulk supplier sells now and we buy it in bulk as well as in qt cases...

In winter I switched most commercial users of Onan's to a 10-30 oil

All air cooled engines work their oil over very hard.

Typical 7kw gas Onan's used in commercial trucks, when the oil is changed it's in bad shape if gone to many hours.....real bad!

Oil does more than lubricate.....it also helps to cool and carry heat away from various engine parts.

The 7kw's develop cylinder head failures from the heat.
Fresh oil helps....
Poor installs kills them and the same goes for the 4kw machines but not as bad.....

Using synthetic oil is not a bad idea but it still needs to be changed often because of how bad it deteriorates from the heat.....