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Dear Car Talk: You often recommend synthetic motor oil for cars. How do they make synthetic oil? Most modern products are made from oil, plastics, etc.
What do they make synthetic oil from? — John
Good question, John. In referring to oil, synthetic means that the process is not a naturally occurring one. But synthetic oil still begins with petroleum.
There are two ways synthetic oil is made. The “from the ground up” method involves starting with crude oil or natural gas, and “cracking” it to remove a small molecule called ethylene.
Then they take these small ethylene molecules and fuse them together and build larger and larger molecules, eventually ending up with something called PAO (polyalphaolefins, not to be confused with KUNG PAO at your local Chinese restaurant)
Then, they mix the PAO with hydrogen to stabilize it and protect it from breaking down in heat and air. And, voila! A very pure oil. That’s method number one.
The more common process goes in the other direction. Instead of starting from the molecular level and building up, they start with crude oil and remove impurities.
Using a chemical catalyst, plus hydrogen, heat, and high pressure, they’re able to weed out impurities like nitrogen and sulfur. The process also rearranges the molecules, and makes the whole thing not only purer, but also more stable and long-lasting. And the result is a pretty close match with PAOs. Then, like any other oil, they add in things like detergents, viscosity agents, and anti-wear chemicals.
The result — regardless of which method they use — is a motor oil that, in my experience, does a far better, longer-lasting job of protecting engines. And the reason it works better is that traditional crude oil comes from its dinosaur ancestors with all different-sized molecules. So, the molecules don’t flow as easily over each other and spread as uniformly over your engine parts.
If you want a visual image, Mobil 1 once likened the molecules in conventional motor oil to “a can of rocks.” Which is also how I used to refer to my brother’s brain.
Whereas synthetic oil, they say, has molecules that are more like “a can of marbles.” And marbles flow more smoothly and coat more evenly than rocks.
Got a question about cars? Write to Ray in care of King Features, 300 W. 57th St., 41st Floor, New York, NY 10019, or email by visiting the Car Talk website at www.cartalk.com.