To protect and maintain the appearance of a new Oak staircase, either a wood varnish, oil or wax can be applied.
Wood waxes have been used for centuries on wooden floors and staircases. Although clear wax polishes are good at retaining the untreated appearance of the wood, they don't offer much durability and can wear quickly requiring frequent re-application of the wax. Wood waxes tend to mark easily with liquid spillages.
Another consideration is that the sheen of a wax increases the more it is buffed. It's worth noting that with repeated 'sock traffic', areas of the stair treads will become more shiny than the surrounding wood as the wax is effectively buffed by the socks.
Wood varnishes offer excellent durability with some such as Bona Traffic HD Anti Slip offering anti slip properties. Using a clear varnish will darken the wood grain giving it a slightly damp-like appearance. Varnishes also enhance the natural character, grain and colouration of the Oak. A good test is to dampen a clean kitchen sponge or cloth and wipe over one of the stairs. This will give an approximation of what the staircase will look like when varnished in terms of colour and tone.
Wood oils also provide excellent durability, are easy to apply and maintain. One of the main benefits of a wood oil is that they are very easy to patch repair if an area becomes worn, scuffed or lightly scratched. The affected area can usually be restored by re-applying a thin coat of oil to the damaged area. As with varnishes, clear wood oils will give a slightly darker, damp like appearance and will enhance the natural colour and grain of the timber. Products such as Osmo Polyx Oil Raw (3044) and Fiddes Hard Wax Oil Natural are designed to counter this keeping the wood looking more like its untreated state whilst still offering the same level of protection. As with varnish, there are anti-slip wood oils such as Osmo Polyx Oil Anti-Slip.
Although an unlikely option for a new Oak staircase, the final option is to paint it with a wood paint that is suitable for staircases. If painting a staircase, it's important to only use a paint that is durable enough to withstand the day to day wear and tear of foot traffic. Paints that are not specifically designed for floors and staircases will soon start to wear or come away from the wood.