The clearence between the filter and the generator lower frame is fine in the off and run position. However while starting and particularly while one holds the off button down the generator shakes violently. This shake causes the oil filter to come in contact with the Onan's lower frame which caves in the bottom of the filter. This condition cannot be seen from a standing or kneeling position, unless a mirror is used.
As we know filters are very thin and it would not be long before this action rubs a hole right through the filter.
The result of which I don't have to explain. Especially when I can find nothing in the manual about a low oil cutoff. A safty feature some generators have. My coach is a 99, the generator has only 47 hrs on it, and the motor mounts are tight, so we are faced with a bad design that requires our constant attention and an extra filter on board.My research suggest the following filters should fit, Onan #122-0645, Purlator #L10241, and STP Deutsch #D366.
Going slow and sharing what we know. George B