Even in 2024, there still exists a lot of questions surrounding synthetic and conventional motor oils. In order to help answer some of the most common questions, AMSOIL has put together a Tech Tips series on their YouTube channel. In this particular episode, AMSOIL’s Technical Product Manager, Len Groom, answers three big questions regarding the difference between synthetic oil and conventional dino juice.

Q: Can you mix synthetic oil with conventional oil?

At the end of the day, if it’s an emergency and you need to do it to get you out of someplace… Yes, you can mix the two types of oil. It won’t create catastrophic damage, be we don’t recommend it. We build synthetic oil with a very fine blend of additives and base oils, and when you throw a conventional oil in there — which is build completely differently — you can throw the mix all off, and the longevity of the oil can be compromised.

Q: The prior owner ran synthetic, but now I’m running conventional oil. Is that safe?

It won’t create any catastrophic damage. There’s no problems with that at all. There’s a myth out there that says, “Once you go synthetic, you can never go back.” That just isn’t true. The engine doesn’t know the difference. As long as you’re not mixing the two, there are no issues. You can switch back and forth between conventional and synthetic oils.

Q: Can using synthetic oil cause my engine to leak oil?

Is it the fault of the synthetic? No. However, to answer that properly, we have to be completely honest. Synthetic oil has a natural detergency. So, if you have an engine that has a pile of miles on it, and you put a synthetic in there, in certain situations, that synthetic can go in there and clean all the dirt out, that’s actually holding the oil in and stopping up any small leaks from a compromised seal. Hence, why high-mileage oil exists. We put in seal conditioners and seal-swell agents to help when it cleans all that gunk out. The seals soften and swell, and you don’t have any leaks. It’s an interesting question, because synthetics get a bad reputation for causing it, when they aren’t really the cause of the leak.

AMSOIL’s High-Mileage synthetic oil exists specifically to handle the needs of an engine that has been around the block a time or two. In addition to a strong synthetic base oil and robust additave package, the High-Mileage formulation also includes seal conditioners to soften up the seals in the oil pan, as well as seal-swelling agents that force the seals to expand and do their job more effectively, without relying on engine gunk to act like an ad-hoc infomercial sealer.