I often read, that leaking motor oil is a major risk for the environment. It is also often said, that motor oil leakages can endanger the drinking water supply for communities. So what exactly are the mechanisms? Sadly I can't find many sources on this. Most websites only mention practical tipps in handling motor oil or just remain vague on the topic. I'd like to know a little more detail about the following questions.

Please notice: This is not about oil spills of crude oil into the oceans. Or a about someone saying oil does not belong into clean earth. I'd like to hear about mechanisms and facts.


  1. What exactly does the damage: Is it the oil? If so would cooking / vegetable oil do the same damage to environment? Or is it the fact, that it is synthetic or mineral oil opposed to organic oil?

  2. What do additives inside the oil add to this topic? Maybe they are the reason, why it is so harmful to environment? If so: Why does no one try to produce motor oil, that does contain less toxic additives?

  3. How is the damage done?

  4. How much damage does oil leakage of motor oil to the environment and society? Is this also contributing to climate change?

Partial answers are welcome. Thanks for clarifying!

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    Whatever the damage ,it is much less than in the past like the 1960's. Oil was then changed at 2000 ,not 6000 or 8000 miles like today. There were dramatically more leaks . There was dramatically more burning; at that time if car burned a quart in 1000 miles , you could say "it did not burn oil". Mineral oil is hydrotreated so not a lot different from baby/mineral oil, I don't know about additives. And , NO, vegetable oil can not be substituted, ideally motor oil is paraffinic . Feb 4, 2022 at 16:13
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    @blacksmith37 Just FYI, Toyota considers it completely acceptable for a Toyota Prius to consume up to 1.1qt of oil every 600 miles (1L per 1000km). Source: Toyota Prius owner's manual page 427. Many Toyota Prius vehicles consume even more oil than that, but to my knowledge, there still has not been any recall or action by any government. Yes, it's disgraceful and unacceptable of Toyota. Feb 6, 2022 at 8:01
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    Every car manufacturer is lying that 1L per 1000km is okay for oil consumption. In reality, well-designed cars consume either no oil at all, or consume it so little that in the 15000km oil change interval, the oil level is above the low mark if it was at the full mark when oil was put there. The car manufacturers want to avoid liability for broken engines. An engine that consumes 1L per 1000km is broken but the car manufacturer won't admit that.
    – juhist
    Feb 6, 2022 at 9:39

1 Answer 1


Here is a document from the National Park Service which summarizes a lot of information about environmental effects of used motor oil. It includes references to many other papers. The primary concerns are toxic organic compounds formed while the oil is in use, and heavy metals that make their way into the oil.

Here are a couple of useful excerpts:

New motor oil contains fresh and lighter hydrocarbons that would be more of a concern for short-term (acute) toxicity to aquatic organisms, whereas used motor oil contains more metals and heavy polycyclic aromatic hydrocarbons (PAHs) that would contribute to chronic (long-term) hazards including carcinogenicity (see Chem.Detail section below). Metals of concern include lead; and often to a lesser degree, zinc, chromium, barium, and arsenic

Aromatics are considered to be the most acutely toxic component of petroleum products, and are also associated with chronic and carcinogenic effects [770]. Aromatics are often distinguished by the number of rings they possess, which may range from one to five [770]. Lighter, :mono-aromatics (one ring) compounds include benzene, toluene, ethylbenzene, and xylenes [771]. Aromatics with two or more rings are referred to as polyaromatic hydrocarbons (PAHs) [770]. Waste crankcase oil contains several toxic components including up to 30% aromatic hydrocarbons, with as much as 22 ppm benzo(a)pyrene (a PAH) [75].


As an oil used in a crankcase, motor oil breaks down to give a wide variety of oxygenated and aromatic hydrocarbons [497]. Other organic compounds found in waste oil include toluene, benzene, xylenes, and ethylbenzene. Also present are organic and inorganic compounds of chlorine, sulphur, phosphorus, bromine, nitrogen, and metals such as zinc, magnesium, barium, and lead resulting from.~oil additives and. contamination during use or disposal [752].

Used engine oil is a contaminant of concern, with large volumes entering aquatic ecosystems through water runoff. The major source of petroleum contamination in urbanized estuaries comes from waste crankcase oil [762]. PAHs, heavy metals, additives and antioxidants, trace levels of chlorinated solvents, and PCBs have been detected in used engine oil [519]. As mentioned above, naphthalene, benzo(a)pyrene, fluorene, and phenanthrene are common PAH components of used motor oil [75].

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