Fill up them tank cars. Linseed oil is a clear to yellowish oil obtained from the dried ripe seeds of the flax plant. It is used as a preservative for wood, concrete, and an ingredient in paints and varnishes. As if that wasn't enough, it is also used in soaps, inks, and in the production of linoleum! It is important to distinguish between linseed oil and flaxseed oil. Although both oils come from the same seed, they are treated differently. Flaxseed oil is raw, cold-pressed linseed oil, and it is often sold as a dietary supplement. Linseed oil is heated and subjected to chemical treatment, and it is not safe to consume.