Rick's Free Auto Repair Advice

Does synthetic oil cause leaks?

The facts — Does synthetic oil cause leaks?

Synthetic does not cause oil leaks?

No, switching to synthetic oil will not cause leaks unless your engine was already leaking oil.

Back when synthetic oil was introduced to the public, owners complained that their engines leaked oil. They blamed the switch to synthetic oil and from that point on, it became a well-known “fact” that switching from conventional to synthetic motor oil caused your engine to leak. But here’s what was really going on.

Synthetic oil was designed for racing

Racing oils don’t contain detergents, dispersants, seal conditioning additives, or anti-corrosion additives. Why? Well, the answer is two-fold. First, they don’t need those additives because the oil in race cars is changed after every race. Second, because those additives take up space. A quart of oil is actually about 75% oil and 25% additives. If you don’t need the additives, and you really need the lubrication, why not get rid of the additives?

The problem came into play when owners started using those early synthetic racing oils in their daily drivers. The lack of seal conditioners and the fact that the oil flowed better at cold startup caused hardened seals to leak oil. That’s where the story got started.

Today’s synthetic oils contain all the necessary additives to prevent leaks.

If your engine wasn’t leaking oil before you switch to synthetic, it won’t leak after the switch. However, if your seals and gaskets were already leaking, switching to synthetic may cause them to leak even more, but only during a cold startup.

©, 2021 Rick Muscoplat

Posted on by Rick Muscoplat

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