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Our planet’s odometer is saying it is time for an oil change

By Anna Kulow As car owners, we secretly dread the moment when the odometer reading matches the number on the sticker in the upper corner of our windshield. Every 5,000 miles or so, we must take an hour out of our busy lives to get an oil change. Most of us trust the mechanic performing...

By Anna Kulow

As car owners, we secretly dread the moment when the odometer reading matches the number on the sticker in the upper corner of our windshield. Every 5,000 miles or so, we must take an hour out of our busy lives to get an oil change. Most of us trust the mechanic performing the task to choose the best oil for our vehicle. But is that always the best choice for our planet?

According to the California Department of Health Services, over 40 percent of pollution in American waterways is from used motor oil. Rivers and streams transport nearly 500 million gallons of used motor oil into our oceans, making it the greatest source of petroleum pollution in the marine environment.

However, motor oil is essential to making a car run smoothly because it prevents the moving metal parts of the engine from actually coming in contact with each other. Instead, they glide along a thin coating of oil, preventing wear and tear. Oil also circulates through the engine, cooling certain parts, such as the transmission. Finally, oil acts to trap particulates and other impurities to keep the engine clean.

The most important characteristic of motor oil is its viscosity, which is its resistance to flow. Oil has a higher viscosity than, say, water or alcohol. Moving an object through oil is a lot more difficult than moving the same object through water. Therefore, the vast majority of motor oils are made from a heavy, thick petroleum-based stock derived from crude oil. Chemical additives are then added to improve certain properties of the oil. When motor oil leaks from vehicles or is improperly disposed of, it is not only the petroleum oil being washed into our waterways, but also a host of chemical additives.

Critical additives in motor oils include a class of chemicals called viscosity index improvers (VIIs). When an oil type has two numbers, such as 10W-30, it means VIIs have been added to ensure the oil remains liquid at a wider range of temperatures. VIIs are made up of large molecules called polymers. Due to their large size, they tend to persist in the environment and float on water surfaces. Although VIIs are generally considered to have low toxicity, few studies have examined their impact on marine wildlife.

Other chemicals added to improve the performance of motor oil include anti-wear and extreme pressure additives, corrosion inhibitors, detergents, and dispersants to minimize sludge build-up, and alkaline additives to neutralize acidic oxidation products of the oil. When used oil is improperly disposed or burned, these chemicals are also transported into waterways. The anti-wear agent zinc dithiophosphate (ZDDP) is well-known to be toxic to aquatic organisms, not readily biodegradable, and is more likely to make its way into waterways and oceans.

What are the alternatives to petroleum-based motor oil and are they any better for protecting ocean life? You have probably encountered one of them: synthetic oils. Synthetic oils were developed in Germany during the Cold War due to limited crude oil availability. There are two types of synthetic motor oil sold today with the base stock being either polyalphaolefin (PAO) or ester. PAO is a large-molecule synthetic hydrocarbon. While it is shown to persist in the environment, it is not readily taken up by organisms due to its low bioavailability. Esters are readily biodegradable in the environment, but 100 percent ester oil has been associated with increased levels of particulate polyaromatic hydrocarbon (PAH) in vehicle emissions, which can then precipitate from the atmosphere into water bodies and cause mutagenic and carcinogenic effects in aquatic organisms.

Photo by Robert Couse-Baker via Flickr Creative Commons (
Photo by Robert Couse-Baker via Flickr Creative Commons (

However, synthetic oils offer several advantages to conventional oils. They have a higher viscosity index and, generally, have higher performance capabilities than conventional motor oil. Therefore, they require lower amounts of VIIs and other additives than petroleum-based oils, meaning fewer chemicals making their way into the environment. Synthetics also provide better engine wear protection, produce less sludge (keeping the engine cleaner), and can last up to 25,000 miles before needing to be changed. So why isn’t everyone using synthetics? The major downside is cost. An oil change using synthetic motor oil can cost up to three times as much as a conventional oil change. However, the longer oil change intervals coupled with the long-term benefits to vehicles and the environment make up for the additional cost.

Recently, lubricant research has been largely focused on bio-based oils derived from plants and other renewable materials. Biosynthetic Technologies, a California-based company is manufacturing a high performance ester-based stock derived from the fatty acids found in plant oil. Their product is renewable, non-toxic, biodegradable, and does not bioaccumulate in organisms. While early-stage plant-derived synthetics had performance problems, new formulations are providing performance benefits matching or exceeding conventional oils, meaning substantially fewer toxic additives need to be mixed in.

Next time you go in for an oil change, consider the impact your choice in motor oil has on the health of our oceans. Ask your mechanic about newer bio-based oils. Although you might not think your choice makes a difference, consider that the average vehicle loses three gallons of used motor oil to the environment. According to the U.S. Environmental Protection Agency, just one gallon of motor oil can contaminate one million gallons of fresh water. Your choices do make a difference in improving the health of our waterways. Our planet’s odometer is telling us it is time for an oil change.


Anna Kulow is a freelance writer based in Solana Beach, Calif. This article is part of the Silent Oil Spills public awareness campaign.

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Meet the Author

Annie Reisewitz is a communications and marketing consultant for environmental and green technology initiatives.