A blendstock is any unfinished oil that is blended with other similar unfinished oils to make a final refined product.

Most blendstocks are produced and used inside the same refinery. However, some are traded in the market, either between refiners or with third-party product blenders.

Blendstocks also referes to components that are not produced from crude oil, such as biofuels, but are blended with oil-based compenents to make finished products.