First published October 2009, updated January 2012

Many people are aware that old engine oil shouldn't be dumped, but recycled. Unfortunately, up to 100 million litres (approximately 26.4 million US gallons) of the stuff is improperly disposed of each year in Australia alone according to our Department of the Environment, Water, Heritage and the Arts. The global figure would be staggering.

It's dumped in household trash, used as weed killer, pour in ditches, left laying about or illegally dumped. Actually, I'm feeling rather guilty as I write this as I have a gallon or so of old oil stashed away (safely) - still - even after over 2 years passing since I first published this article.

Used engine oil is incredibly toxic stuff and a gallon can contaminate one million gallons of water. Pouring it on land doesn't reduce the risk either as it can seep down into the water table as well as rendering the soil incapable of sustaining plant life.

Used oil doesn't wear out - it just gets filthy. It can be cleaned of contaminants and recycled continuously. It can even be cleaned to the point where it can be reused as engine oil.

The dirty oil goes through the same refining process as oil that is extracted from wells, so it's not exactly a "green" process, but it doesn't have the added environmental impact of the extraction. 

New engine oil made from recycled oil meets the standards used in the industry lubrication industry. According to the American Petroleum Institute, re-refined oil is of as high a quality as a virgin oil product.

The recycling process is as follows:

- Removal of any water
- Filtering to remove solids and additives
- De-asphalting to remove bituminous content
- Distillation

Environmental benefits of recycling used engine oil

Information from the USA Environmental Protection Agency states that re-refining used oil takes only about one-third the energy of refining crude oil to lubricant quality. It takes 42 gallons of crude oil, but only one gallon of used oil to produce a half gallon of new, high-quality lubricating oil that can be used in car engines.

While only around 0.9% of crude oil consumption in the USA is in the form of producing lubricating oil, when you consider the US chewed through well over 18 million barrels a day in 2010, it still amounts to a lot. 

Some quick, back of virtual envelope calculations:

18 million x 365 = 6,570,000,000 barrels a year
6,570,000,000 barrels a year x 42 gallons = 275,940,000,000 gallons
0.9% of 275,940,000,000 = 248,3460,000

So, around 248 million gallons of oil is used each year for lubricating engines and machinery based on the 18 million barrel a day figure.

If all that was recycled, it would mean 124 million gallons, or 2.9 million barrels that wouldn't need to be extracted each year. It's not an insignificant amount - both in environmental and economic terms.

Other uses for recycled engine oil

While the following uses may not be all that "green", it goes to show just how important that this resource is recycled rather than just thrown out. By recycling engine oil, we reduce the need for extraction of crude oil and the associated environmental impacts of that activity.

- Engine oil can also be used as fuel oil. By recycling just two gallons of used oil, it has the energy potential to generate enough electricity to run the average household for almost 24 hours. One gallon of used oil processed for fuel contains about 140,000 British Thermal Units (BTUs) of energy. 

- It can be reused as hydraulic oil

- Many petro-chemical based products such as plastics can be made with it

Where to recycle engine oil

To find out where you can recycle engine oil in the USA, try Earth911.org and search for a collection center via zip code.

In Australia, for further information on used oil and to find your nearest used oil collection facility, contact oilrecycling@environment.gov.au or call 1800 982 006

If you're in Canada, try the Used Oil Recycling site for information on collection points.

For folks in the UK, visit Oil Bank Line.

Equally as important as recycling engine oil is to buy products made from the stuff. After learning more about it, I'd have no hesitation in using recycled engine oil it in my car if it was offered as long as it was certified as meeting industry standards. Perhaps its something to have a chat to our mechanics about.