You need to maintain your outdoor furniture properly to keep it in the best condition. You are required to store and clean the furniture properly. You are supposed to install a wide and durable cover to provide additional protection to your furniture. You are likely to store it during winter or harsh weather.
The severe stains are likely to be removed by using mild cleaning soap and soft bristle brush.
On the other hand, the oiling and sending are also likely to be resorted for some serious stains. Thus, you will easily be able to take care of your furniture properly.