Petrol is a wonderful cleaner, esp for cleaning paint brushes (if you have been using oil based paints obviously) better than any paint brush cleaner or white spirit and much cheaper. And as been mentioned up thread, a great degreaser. But super amounts of care are needed with it, on top of the obvious fire/explosive risk the benzene's that are added to it are very poisonous and cancerous, it is not something you want on your skin. (or in your mouth if siphoning, something that has happened to me many times when I was younger)
As for containers, I regularly fill a plastic container at the filling station for the lawn mower and chain saw, only once in te last 30 years was I refused on the grounds it was not a specific fuel container.