This is going way back to the early days of my solar power experience, I was the only one to have solar panels in this area. These are from the Arco solar power generating plant Carrizo Planes California. They used mirrors to get more power out of them thus the brown color.
So it was time to change oil in the diesel generator and I put a pan under the drain hose opened the valve and walked away from it only to find the oil over flowing the drain pan half hour later. If I had to do it over again I would have fabricated and installed a drain pan under the whole generator just for things like this.