Some choices of Cutting Board Oils
Mineral oil – Mineral oil is a popular choice as it is the cheapest food-grade oil you can buy (do not use vegetable or olive oils because they turn rancid faster than others). Mineral oil remains safe throughout its life. There are various oils marketed for cutting boards and butcher blocks with fancy names like "Butcher Block Finishes" or "wood Butter”...save some money by visiting the local hardware or drug store and purchasing Mineral Oil (not mineral spirits - that is paint thinner).
Walnut Oil – This is an all-natural oil and is one of the few oils that does not turn rancid as easily as other oils. However, all natural oils will go rancid eventually. Personally, this is my preferred oil, but I don't use it ONLY because some people have an allergy to nuts or nut products. If not for the allergy this is very good oil for wood cutting boards (or any wood project).
Coconut Oil – Some research and experimentation have been conducted and found that food-grade coconut oil/butter also works great. It can also be used for seasoning Cast-Iron Pots and Pans. Coconut oil is one of the most stable oils and is highly resistant to rancidity. It is stable because of its high proportion of saturated fats. Coconut oil has a long shelf life of two or more years, and does not have to be refrigerated. Coconut oil should be stored out of direct sunlight. If you live in a hot climate, it is recommended to store unused coconut oil in the refrigerator. However, I have not personally even tried it yet, so I can’t attest to its viability.
Beeswax Top Coat - A beeswax top coat is an optional addition to the re-finishing process, but is well worth the time. Beeswax gives a tougher finish. The beeswax sits on the surface of the wood in contrast to the oil that soaks into the wood. As a result the wax fills in pores and gaps that thin oil can't bridge. This helps to keep moisture, bacteria, and other contaminants from getting into the wood surface. It will make wood water-resistant (though not water-proof) and will help protect the wood surface from use and wear. It will give you a shiny smooth surface and male the surface more water resistant. You’ll want to give your board a refresher of this oil/wax combo periodically.
KEEP YOUR WOOD CUTTING BOARD DRY! All cutting boards, and other food surfaces, should be kept dry when not in use. Resident bacteria survive no more than a few hours without moisture. Keep moisture of any type from standing on the block for long periods of time. Beware of moisture collecting beneath the board if you leave it on the counter. Absolute best method of storing – prop one end up when not using your board.