Changing Planet

Heavy Metals in Motor Oil Have Heavy Consequences

By: Annie Reisewitz and Sarah Martin

We’ve all heard the old adage, “Oil and water don’t mix.” Yet we are constantly mixing the two, it seems, hoping that one day they will indeed mix. Add in drought and pollution and the potential environmental problems grow even larger.

Every year 10 billion gallons of liquid petroleum, in the form of motor oil and other industrial lubricants, are released into the environment due to human activity. But how does that oil affect the quality of our water supply, especially in severe drought regions like California?


Tanker source flow from tree line. Photograph from Flickr Creative Commons
Tanker source flow from tree line. Photograph from Flickr Creative Commons

As motor oil circulates through a car’s engine it picks up heavy metals such as arsenic, lead, cadmium, copper and zinc, as well as other toxins. The U.S. EPA considers all of these to be priority pollutants, toxins that, according to the Clean Water Act, are a high priority for development of water quality control measures and discharge limitations because they are frequently found in wastewater.

As the drought shrinks useable freshwater supplies, heavy metal contaminates in motor oil concentrate, further jeopardizing our drinking water supply. Another concern is that, as these toxic pollutants enter our waterways, they are consumed by smaller fish, eventually cascading up the food chain in larger concentrations before entering our bodies from the fish we eat.

The extent by which these toxins are entering stormwater runoff and polluting lakes, rivers and oceans downstream are largely unknown. However, we do know that one gallon of motor oil can pollute one million gallons of water. The average car loses two gallons of oil a year from normal use, and one gallon is lost through improper disposal. This means we are potentially polluting three million gallons of water per year, per car, and there are 253 million cars and trucks on U.S. roads. That’s a very large, and very silent, oil spill.

A residential fuel oil spill and associated assessment activities in Beverly, Massachusetts. Photograph from Flickr Creative Commons.
A residential fuel oil spill and associated assessment activities in Beverly, Massachusetts. Photograph from Flickr Creative Commons.


Used oil, generated by its use as a lubricant in automotive vehicles and in industrial operations, constitutes about one third of California’s hazardous waste stream. Preventative actions must be taken to ensure that used petroleum motor oil filled with heavy metals doesn’t enter our water supply. The best ways to achieve this is by properly disposing used oil, through recycling and the use of bio-based motor oil and synthetics.

According to the EPA, lubricant base oils derived from minerals (i.e. petroleum) “have the lowest biodegradation rate, a high potential for bioaccumulation, and a measurable toxicity toward marine organisms.” In contrast, motor oils derived from oleochemicals (e.g. vegetable oils and synthetic esters) degrade faster, do not bioaccumulate appreciably and have a lower toxicity to marine organisms.

Many environmentally friendly, bio-based motor oils exist today. Emerging clean automotive technologies, fully certified by the American Petroleum Institute (API) to meet the specifications of automakers, are biodegradable, non-toxic and will not bioaccumulate in marine organisms. They are also recyclable along with mineral oils in the current collection systems already in place. In Europe, bio-based motor oils are ubiquitous and government-based incentives, such as the EU EcoLabel for lubricants, encourage motor oil manufacturers to develop and sell motor oils that are less harmful to the environment. Despite recent surveys that say 50 percent of Americans care about what brands are doing to help the environment, the U.S. is light-years behind the EU in the widespread adoption of environmentally friendly motor oils.

Environmentally acceptable lubricants, as they are referred to by the U.S. EPA, are in many cases are cleaner on your car’s engine as well as the environment. Alternatives to conventional petroleum oil products should be given a chance to compete in the marketplace without the interference of special interests.

Currently, the California Assembly is reviewing a bill, AB 628, which, if enacted, would encourage solid waste source reduction and the production and use of more environmentally acceptable motor oils and lubricants in California.

Our coalition seeks to bring public attention to the impacts of motor oil pollution. If passed, AB 628 will send signals to the marketplace to research, develop and move motor oil to be safer, cleaner and more sustainable. Let’s be a world leader in the adoption of non-petroleum alternatives and encourage the widespread use of clean, environmentally friendly motor oil.


About the authors:

Annie Reisewitz is a communications and marketing consultant for environmental and green technology initiatives. She manages the Silent Oil Spills public awareness campaign. 

Sarah Martin has worked in environmental communications for the past several years. She works on the Silent Oil Spills campaign.


  • Prince Arora

    You have discussed an interesting topic that everybody should know. Very well explained with examples. I have found a similar
    website pcb transformer removal visit the site to know more about coopersenviro.

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (

Social Media