Many ovens have a convenient window so we can see the progress of cooking. However, after time, the glass becomes greasy making visibility dim. Like you, I’ve cleaned the glass inside and out, to no avail. The problem is between the panes of glass. My friend Nancy told me that there is a simple way to clean between those panes of glass! This is such a breakthrough as I thought the only way in was with a screwdriver! Open the drawer underneath the oven door. Then feel under the bottom of the closed oven door. There is an opening large enough to slide in a cleaning tool. Be sure to use a one-piece cleaning tool as you don’t want anything to disconnect or get stuck between the glass. See the photo for a better description. I am so thrilled with this tip! Thanks, again Nancy!