Do I need to use teak oil or other products on my outdoor teak furniture?
Not really. Teak oil will help preserve the brown color longer by slowing down the graying process. It will not stop it. It is okay to use teak oil, but it is certainly not required to maintain your teak furniture.
When using teak oils, make sure that the product does not have any tint or color. Test the product on the underside or other inconspicuous spot to make sure you are okay with the color.