Photo: Jason Torchinsky

As someone who finds himself covered in automotive filth quite often, I decided to do some research to see just how dangerous all the fluids in my car are—you know, just to have a better idea of how many years I’ve got left to live. My conclusion: probably not many.

Your car, as you may know, runs on a variety of liquids, from motor oil to transmission fluid to windshield washer fluid. All of them are, in one way or another, not things you should ingest. I sought to learn just how toxic all of them are.

The first thing I did was call up my local Occupational Safety and Health Administration office, and they told me to check out material safety data sheets for each of the fluids that regularly stain my clothing. So, in the laziest form of research ever, I simply Googled the name of the products, followed by “Material Safety Data Sheet,” and to my surprise, that data is readily available. In fact, most any website that sells any automotive fluid will include the SDS near the product description.

In these Safety Data Sheets, I found the health implications of each fluid, and was left with an overwhelming desire to invest in a couple Hazmat suits.

Motor Oil


After wearing clothes dyed in motor oil, and eating off plates covered in the stuff, I was told by readers that I’m probably going to die soon. Keen to put those readers (and also my worried mother) at ease, I looked up the material safety data sheet for a couple of fluids, including synthetic Mobil 1 10W-30 and conventional Pennzoil 10W-30.

The first thing I found was that motor oil seems pretty harmless when it’s clean, with the Pennzoil data sheet agreeing with the Mobile1 sheet, which says inhalation, ingestion and exposure to skin are “Minimally Toxic.”

In fact, clean oil is so safe that the data sheets even said you don’t need to worry too much about skin protection. Here’s the quote from the Mobil 1 document:

No skin protection is ordinarily required under normal conditions of use. In accordance with good industrial hygiene practices, precautions should be taken to avoid skin contact.


The only even remote worry, based on Pennzoil’s safety data sheet, is that the oil could clog up your pores and give you a bad case of pre-teen acne:

Prolonged or repeated skin contact without proper cleaning can clog the pores of the skin resulting in disorders such as oil acne/folliculitis.

It also mentions that nausea, vomiting and diarrhea could result if you drink too much, and both sources say “mild, short-lasting discomfort to eyes” could occur if a gob of the stuff gets past your safety goggles. But in the end, clean motor oil really doesn’t seem so bad.


Mobile 1 Synthetic MSDS shows that, when clean, oil isn’t too dangerous.

Then I got to the section about used motor oil, and things became much less pleasant. The data sheets say that, when oil is dirty—like it was when I wore and ate it—it becomes a carcinogen. Here’s what the Mobil 1 synthetic data sheet reads:

Oils that are used in gasoline engines may become hazardous and display the following properties: Carcinogenic in animal tests. Caused mutations in vitro. Possible allergen and photoallergen. Contains polycyclic aromatic compounds (PAC) from combustion products of gasoline and/or thermal degradation products.


And here’s Pennzoil’s remarks, describing why used oil is so much more dangerous than clean oil:

Used oils may contain harmful impurities that have accumulated during use. The concentration of such impurities will depend on use and they may present risks to health and the environment on disposal., ALL used oil should be handled with caution and skin contact avoided as far as possible. Remarks: Continuous contact with used engine oils has caused skin cancer in animal tests.

So basically, wearing clothes with dyed in oil and eating off of dishes with films of oil all over them really isn’t that bad. Unless the oil is dirty, in which case it is quite a terrible idea.


Engine Coolant

Arguably the most dangerous fluid in your garage is engine coolant, also called antifreeze. It contains a sweet, syrupy fluid called ethylene glycol, which acts to raise the boiling point and lower the freezing point of the water used to cool the engine. Though this green, pink, or yellow fluid looks harmless, it can be deadly.


Prestone Antifreeze safety data sheet shows the danger of ingesting coolant.

Prestone’s safety data sheet shows that, if you drink coolant, you’ll be in a world of hurt. It says in the “Most Important Symptoms” section:

Ingestion may cause abdominal discomfort or pain, nausea, vomiting, dizziness, drowsiness, malaise, blurring of vision, irritability, back pain, decrease in urine output, kidney failure, and central nervous system effects.


Malaise? Kidney failure? Central nervous system effects? This sounds terrible. It goes on in the “Notes to Physician” section, saying:

There may be cranial nerve involvement in the late stages of toxicity from swallowed ethylene glycol. In particular, effects have been reported involving the seventh, eighth, and ninth cranial nerves, presenting with bilateral facial paralysis, diminished hearing and dysphagia.

That’s right: the seventh, eighth and ninth cranial nerves. Those are the best ones! (I have no idea what those are). Also, facial paralysis? Diminished hearing? There’s no way this could possibly get worse.


But it can. The data sheet goes on to say that cardiac failure and pulmonary edema could also result from ingesting too much coolant, and in the “Chronic Effects” section, it says this about inhalation:

Prolonged or repeated inhalation exposure may produce signs of central nervous system involvement, particularly dizziness and jerking eye movements.

Jerking eye movements? Geez. But there’s more:

Ethylene glycol has been found to cause birth defects in laboratory animals. The significance of this finding to humans has not been determined. 2-Ethyl Hexanoic Acid, Sodium Salt is suspected of causing developmental effects based on animal data.


So basically, if you drink or inhale enough coolant, you might screw up your brain, your heart might fail, you could lose feeling in part of your face, get a twitchy eye, lose your hearing, suffer kidney failure, get blurry vision, and, if you’re pregnant, potentially develop birth defects in your unborn child. Don’t drink or inhale coolant, then!

The good news is that touching coolant or getting into your eye is relatively safe. So there’s that

Windshield Washer Fluid


Windshield washer fluid is about one third methanol by weight, and methanol is very unpleasant stuff. I looked up the safety data sheet for Splash and Peak, two very common washer fluid sold in the U.S., and found that, like antifreeze, inhaling or ingesting washer fluid could lead to kidney, central nervous system or optic never damage.

The Splash data sheet indicates that inhalation is the biggest danger when it comes to washer fluid, saying:

Acute exposure of humans to methanol by inhalation or ingestion may result in visual disturbances, such as blurred or dimness of vision, leading to blindness. Neurological damage, specifically permanent motor dysfunction, may also result.


The sheet also says that the fluid is toxic by “inhalation, in contact with skin and if swallowed,” and that “Amounts as small as 30-250 mL of pure methanol may be fatal,” though it doesn’t say exactly how much washer fluid that translates to.

The Peak data sheet breaks down the heath effects, saying that through skin absorption, “harmful quantities of Methyl Alcohol may affect eyes and central nervous system,” through inhalation, “high concentrations may cause acute central nervous system depression characterized by headaches, dizziness, nausea and confusion.”

And finally, the data sheet discusses ingestion, saying:

May cause nausea, abdominal pain, headache, shortness of breath, visual impairment and blindness. Severe poisoning can cause coma and death.


It continues:

Ingestion of large amounts of Methyl Alcohol has been shown to damage organs including liver, kidney, pancreas, heart, lungs and brain. Although this rarely occurs, survivors of severe intoxication may suffer permanent neurological damage.

So I take it back when I say coolant is the most dangerous fluid in your car, because washer fluid is right up there with it.


Gear Oil

I looked up both synthetic and conventional Valvoline gear oils that you’d find in your differential, and they seem relatively safe, with the “Most important symptoms” section applying only to high amounts of breathed-in oil vapors:

Acute aspiration of large amounts of oil-laden material may produce a serious aspiration pneumonia. Patients who aspirate these oils should be followed for the development of long-term sequelae. Repeated aspiration of small quantities of mineral oil can produce chronic inflammation of the lungs (i.e. lipoid pneumonia) that may progress to pulmonary fibrosis.


It goes on:

Symptoms are often subtle and radiological changes appear worse than clinical abnormalities. Occasionally, persistent cough, irritation of the upper respiratory tract, shortness of breath with exertion, fever, and bloody sputum occur. Inhalation exposure to oil mists below current workplace exposure limits is unlikely to cause pulmonary abnormalities

The datasheets also mention that exposure through inhalation, swallowing or the skin can include nausea, vomiting and diarrhea, as well as irritation in the nose, throat and airways. The synthetic fluid also mentions acne and “serious eye irritation,” while the conventional fluid mentions headache, dizziness, and potential for an allergic skin reaction.


Automatic Transmission Fluid

Automatic transmission fluid is essentially a light oil that is also “reasonably” harmless based on the Valvoline Maxlife Dex/Merc safety data sheet. The health risks associated with it are almost exactly the same as those of the gear oil mentioned above.


Power Steering Fluid

Quaker State’s Power Steering Fluid safety data sheet basically outlines the same health risks as those mentioned in the automatic transmission fluid and gear oil sections above, namely potential respiratory issues when inhaled, and diarrhea if ingested.


Brake Fluid

Brake fluid contains similar ingredients as antifreeze, so it should be no surprise when Prestone’s DOT 3 material safety data sheet mentions that their product could cause eye damage, skin irritation, and damage to kidneys and liver through prolonged or repeated ingestion.


In the “Most Important Symptoms” section, the data sheet says eye contact could cause corneal injury, and that skin exposure could yield “mild skin irritation or sensitization.” It goes on, discussing the effects of breathing brake fluid’s vapors, saying:

Breathing high concentrations of vapors or mists may cause irritation, headache, dizziness, drowsiness, nausea, loss of sense of balance and visual disturbances.

Then it talks about what happens if you drink brake fluid:

Swallowing may cause gastrointestinal disturbances including irritation, abdominal pain, back pain, nausea, vomiting, diarrhea, headache, dizziness, drowsiness, nausea, visual disturbances, decreased urine production, malaise, unconsciousness and liver or kidney damage.


Then at the bottom, the data sheet says that contact with damaged skin could lead to “absorption of potentially lethal amounts.”

R134a Refrigerant

Photo: Amazon


You know those little bottles of refrigerant you use to “charge” your air conditioning system? Well, they’re not particularly good for your health.

The material safety data sheet for the can of A/C Pro in the picture above, says that inhaling the R134a refrigerant inside can not only cause cancer, can also “cause anesthetic effects including dizziness, weakness, nausea, to unconsciousness.”

The refrigerant can actually replace oxygen in your blood and cause asphyxiation, and in high doses, can cause “abnormal heart rhythm which is potentially fatal.”


Be Careful With Automobile Fluids!

The fluids mentioned here are normal, everyday automotive items you’d find in an average garage. And while the health effects mentioned here mostly apply to extreme exposures, they’re daunting.

Even though clean motor oil, automatic trans fluid, gear oil and power steering fluid are relatively harmless, coolant, washer fluid and brake fluid can do all sorts of damage to the human nervous system, kidney and liver. And used motor oil and refrigerant can cause cancer.


I, for one, have been humbled. And with some of the terrible effects mentioned, I may never wrench again. Or at least I’ll take extra caution not to eat this stuff.