Is mixing mineral and synthetic motor oils safe?

Mixing mineral and synthetic motor oils in error is relatively easy, but what are the consequences? Is it possible to safely change from regular crude based motor oil to full synthetic engine oil?

What the experts say about mixing mineral and synthetic motor oils?

Here's the current thinking on the subject of mixing mineral and synthetic motor oils. This information is based on the answer to a technical question posted on a popular oil manufacturers website:

There is no scientific data to support the idea that mixing mineral and synthetic motor oils will damage a modern engine. However, when switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because mixing mineral and synthetic motor oils is for the most part, compatible. (The exception is pure synthetics. Polyglycols don't mix with normal mineral oils.)

There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.

There was a time, years ago, when mixing mineral and synthetic motor oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal materials have taken care of those issues.

Mixing mineral and synthetic motor oils could affect older oil seals.

And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what additives the oil companies put in their products.

The question of mixing mineral and synthetic motor oils comes up a lot from people who've just bought a used vehicle and are wanting to start their history with the car on fresh synthetic engine oil.

In general; if the engine is in good working order and not be leaking right now modern synthetic oils should work well. However fully synthetic oils could affect older elastomeric materials that engine seals are made from, so it’s best to stay away from these.

If you’re concerned about mixing mineral and synthetic motor oils it’s always wise to seek expert advice from a professional company, such as Habot Oil. The experts at Habot Oil are well qualified to give expert advice