Yes, most oils will darken the wood once applied. While it will not change the color of the wood, it will make it a shade darker. This has the effect of bringing out the grain and making it far more visible. However, the overall darkening effect of an oil-based finish will keep it from gaining too much contrast.
Not only does oil darken most wood, but this darkening process also gives you an easy way to know when your wooden furniture needs more oil. When you see a pale spot of wood, you know that it’s thirsty, and oil is its favorite drink.