The Full Story
If you read the back of a motor oil container, you will likely find stern warnings indicating that drinking motor oil could be fatal. This is true. However, why it is true has more to do with the physical characteristics of motor oil than its chemical makeup.
Motor oil belongs to a large class of compounds called hydrocarbons. In their simplest form, hydrocarbons are combinations of carbon and hydrogen atoms. There are many varieties of hydrocarbons, but all hydrocarbons tend to feel oily to the touch when in their liquid state. When these oily substances are swallowed, the worry is that they can slip into the airway or be inhaled later during the process of vomiting. This is called aspiration, which can be very irritating and lead to infection. The airway is right next to the food pipe, and the close proximity is the reason aspiration happens. The ease of which a substance can flow is the characteristic known as viscosity. Low viscosity (thinner) hydrocarbons are more likely to be aspirated than high viscosity (thicker) hydrocarbons.
When a small amount of motor oil is swallowed and goes down the food pipe into the stomach, the only symptom that is expected is a laxative effect (loose stools or diarrhea). This type of exposure can be safely watched at home. However, if motor oil is aspirated or suspected of being aspirated, the person should be taken to an ER for evaluation. A product might have been aspirated if the person coughs (as if something has gone down the airway) or vomits. In the ER, the patient will be evaluated and typically have a chest x-ray to look for any inflammation in the lungs.
Used motor oil has contaminants that are not present in new motor oil. When a car is running, motor oil is exposed to high heat, which creates new chemicals that are more toxic. Additionally, while circulating through the car machinery, motor oil collects metal contaminants. Always recycle or properly dispose of motor oil to avoid polluting the environment with these contaminants. Used motor oil also has the risk of aspiration. The addition of contaminants, although toxic, would not change the management of the aspiration. A one-time unintentional exposure to used motor oil without aspiration is not expected to cause any additional toxicity.
Like all hydrocarbons, motor oil can cause defatting of the skin. Defatting is the dissolving of oils and fats in the skin. It can feel like dryness or irritation after direct skin contact with motor oil. If you get motor oil on your skin, wash well with soap and water as soon as possible. A mild lotion can be used to help with the dryness.
If you think someone has been exposed to motor oil, immediately call Poison Control at 1-800-222-1222 or check the webPOISONCONTROL® online tool for help. Whether you call or log on, expert assistance is available 24 hours a day.
Pela Soto, PharmD, BSHS, BS
Certified Specialist in Poison Information
Effects of skin contact with chemicals: guidance for occupational health professionals and employers [internet]. Cincinnati OH: Centers for Disease Control and Prevention and National Institute for Occupational Safety and Health; August 2011 [accessed Jul 13, 2017].
Gummin D. Hydrocarbons. In: Hoffman R, Howland M, Lewin NA, Nelson LS, Goldfrank L, editors. Goldfrank's toxicologic emergencies. 10th ed. New York: McGraw Hill; 2014. p. 1334-45.
Hydrocarbons and motor oils (used). POISINDEX® System [Internet database]. Greenwood Village CO: Thomson Micromedex; updated periodically [accessed Jul 13, 2017].
Irwin, RJ. 1997. Environmental contaminants encyclopedia: oil, used motor oil entry [internet]. Fort Collins CO: National Park Service, Water Resources Division; July, 1997 [accessed Aug 29, 2017].
- Motor oil and many other products in the garage can be deadly. Keep all products up and away from children and pets.
- Motor oil ingestions often happen after transferring it from its original container to another. If you need to transfer motor oil out of the original container, make sure the new container is clearly labeled. Dispose of the new container immediately after use.
- If motor oil is swallowed, do not induce vomiting. Inducing vomiting could cause a nontoxic ingestion to be toxic and cause the need for ER care.
- Follow the guidance from local environmental agencies for disposal of used motor oil.
This Really Happened
Case 1. A mother called Poison Control from her car. She had just arrived at her home and found that her 23-month-old child in the back seat had been playing with a bottle of motor oil. The child was able to open the bottle, the motor oil spilled, and there was some on the side of the child's face. The child had no symptoms of coughing, choking, or vomiting.
Poison Control instructed the mother to give the child something to eat and drink and wash all exposed skin well with soap and water. The Poison Specialist explained the risk of aspiration and gave instructions to monitor the child for respiratory symptoms or fever for the next 24 hours.
The following day, Poison Control called back to check in on the child. The child remained symptom free.
Case 2. The mother of a 2-year-old girl was embarrassed to call Poison Control after her daughter took a sip of motor oil. She immediately searched online for the webPOISONCONTROL tool, and in just 55 seconds, entered the child's age, sex, exposure route (mouth), and indicated no symptoms had developed. The immediate online recommendations (which were also emailed to her) included home treatment, symptoms to expect, and more worrisome symptoms that should prompt a call to Poison Control. She used the online follow-up module the next day to indicate that the child never developed symptoms.