Take it to an authorized dealer and get it checked. Had a similar Onan on our 2001 Adventurer that leaked oil. They said an internal seal where two halves of the engine came together (?) had disintegrated over 1/4 of its length.
Sorry I cannot be more specific - that's what I was told. Was repaired under warranty and did not leak again.
Similar timeframe on MH and gen set. Could both problems be similar?
'14 Winnebago Vista 35F, '14 GMC Terrain
BlueOx Towing Pkg, SMI Stay-n-Play
49 States & 7 Provinces visited in MH | WIT W112365