Well there are 2 things, the compartment itself and the gen. I would clean the compartment with whatever works, degreaser etc. However I would not use a high pressure hose or degreaser on the gen itself. Maybe spot cleaning the gen with something on a rag but I would hesitate spraying it down with anything (water or degreaser). I was told by Onan never to spray with degreaser. The seals on the board will totally degrade. Mine is newer though and have no idea what yours is.