Sealing an outdoor wooden bench is the number one way to extend its life. While some wooden benches come treated and sealed, many do not. Luckily, sealing an outdoor bench is pretty easy. All you need is an oil treatment, such as teak or linseed oil. You can buy a single-coat sealer or if you prefer, an oil-based spray. Apply according to directions, and make sure you treat your bench at least once to twice a year. Even the best seals don’t last forever.