I found the window, however, it's at the very bottom. Heck, you put hardly any oil in it at all and the window is covered. Just below the fill cap is stamped1600 ml which converts to a hair over a quart and a half. Could that be what it holds? I don't know why else it would be there. Also, the window is so cruddy on the inside that I can't even see through it. I'm going to drain the oil and start from scratch. Wondering if a good synthetic oil would work best in it?