Should I Use Motor Oil & Diesel Fuel to Seal & Treat Wooden Fence Posts?

Chemical Free Homestead Frugal Homesteading

Is it DANGEROUS, or are we PARANOID?

Throughout the mid and late 1900’s, many farmers found a way to reuse what they had on the farm, including motor oil. They would up-cycle it into a wooden fence post treatment to prevent wood rot, and to keep insects from eating and burrowing into the wood. The oil kept water from penetrating the wood, and deterred nature’s decomposers (such as bacteria and fungi, like mushrooms) from doing their jobs. The longer the fence post lasted, the less likely it was that the fence post would need replacing in the next 10 to 15 years. In addition, the fence as a whole was far stronger; this prevented livestock from breaking the fencing and running loose. Many also used diesel fuel mixed with the motor oil, as they believed it assisted in preventing the posts from rotting. It performed much like creosote did to preserve posts; which made the farmers rather happy.

However, back then, many farmers weren’t quite environmentally conscious. With all of the controversial farming methods running rampant, including factory farming livestock and conventional farming with row crops and heavy chemical fertilizers, sealing fence posts didn’t seem like a big deal.

Are Motor Oil and Diesel Fuel Sealed & Treated Fence Posts Harmful for the Environment & Food Supply?

Before we dive in, it is worth mentioning that treated wooden posts commonly contained arsenic and creosote; since motor oil does such a wonderful job of sealing and treating wooden posts, you can only assume that it is harmful to the environment and your land. Clean motor oil is considered most hazardous to aquatic life, for a short time. However, used motor oil is far more dangerous. It is known to contain lots of pollutants, including heavy metals such as:

  • Lead
  • Arsenic
  • Chromium
  • Zinc
  • Barium

In addition to these heavy metals, there are also polyaromatic hydrocarbons; which can make up 30% of this used oil. These hydrocarbons can linger for several years within the environment, especially within sediment in streams. While toxicity regarding humans are limited due to inconsistencies, there has been a link between these compounds and an increase in lung, skin, and bladder cancers. In animals, however, studies have proven that certain polyaromatic hydrocarbons can cause a variety of problems. Reproductive systems, immune systems, and even the nervous systems have been affected in various ways, even leading to significant developmental differences. As for cancerous effects on animals, one PAH in particular has proven to be a leading culprit: Benzo(a)pyrene. This particular hydrocarbon can be found in significant amounts in that motor oil that is used to treat posts: as much as 22 PPM!

In short, I would definitely say that treating fence posts with motor oil is rather dangerous. This is especially true when using wooden fencing for cattle, goats, pigs, sheep, horses, chickens, or any other animal that is being raised for human consumption.

Are Pressure Treated or Commercially Treated Fence Posts Any Safer?

This answer could go several different ways. While today’s chemically treated wood is not as dangerous as it was 30 or 40 years ago, it is still loaded with questionable compounds. However, pressure treated wood is simply required sometimes; such as for building large structures that will have significant demands placed on them through the unforgiving weather. Some things can be necessary evils, where as others find ways around using treated wood to further protect our environment. While I advocate treating our beautiful Mother Earth with tender love and care, I will not chastise others for their homestead needs either. I do feel it is better to use previously treated wood, but there is one other option, too! (which we will cover momentarily).

For your animals that produce meat, dairy, and eggs, I recommend keeping all pressure treated wood surfaces out of their reach. If at all possible, try to minimize pressure treated wood use; perhaps for corner posts, the primary “skeleton” of a building, or for the “feet” of a structure that will be prone to rotting quickly. For your gardens and raised beds, try to keep pressure treated wood out of all edible gardening landscaping. This includes retaining walls, pathways, and trellises; anything that could eventually cause contaminated water to reach the roots of those plants.

Natural Ways Around Wooden Post Decomposition and Rotting

Instead of opting for chemically treated fence posts, you can go au-naturale and choose a rot resistant wood. A strong, durable, rot and insect resistant tree species could keep your fence problem free for a very long time, making you wonder why you contemplated using pressure treated posts in the first place.

  • The first wood that comes to mind is Eastern Red Cedar. This wood is incredibly resistant to rot and pest damage! Many claim to have fence posts on their land that have outlived several generations of livestock, some lasting longer than 20 years!
  • Another excellent candidate is Osage Orange or Hedge Apple. Osage Orange is an incredibly hard and durable wood, that isn’t prone to much shrinking like other woods tend to be. You might find that this particular wood can be hard to install fencing hardware on, as well.
  • White Oak is also a very durable type of wood, and highly suitable for fencing. However, White Oak may not be as common as Eastern Red Cedar or Osage Orange.
  • Black Locust wood will last a long time, but it is advised to debark the wood in order to prevent rotting when the post is back filled with earth. A debarked post will withstand the changing seasons and heavy precipitation far more easily.

Have You Given Natural Posts a Go?

If you have used untreated fence posts on your homestead or farm with success, feel free to leave some words of encouragement and tips or tricks for our future readers! Many new homesteaders may not realize just how resilient the wood of many of our native tree species is! In the below video, you can see some locust wood being split for use as fence posts for an electric hog fence.