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WILL I HARM MY ENGINE BY MIXING SYNTHETIC OIL and MINERAL OIL
By: Dan Arcy, Global OEM Technical Manager, Shell Global Solutions
No you will not.
No, you will not. This is an all too common misconception, and one with no scientific data to support it.
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 synthetic oil and mineral-based motor oil are compatible with each other.
There is no problem with switching back and forth.
And to be clear, there is no problem with switching back and forth between synthetic and mineral based oils.
In fact, many of our customers who operate 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 switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time.
Some operators experienced problems with seal leakage and high oil consumption but changes in additive chemistry and seal material have taken care of those issues.
Why change oils from mineral to synthetic? The biggest benefit of changing to synthetic motor oil in the winter is improved start-ability, which is the ability of a vehicle to pull away from a dead stop on a grade. While conventional oil gets thicker in colder temperatures, synthetic oil maintains its viscosity ensuring greater oil flow in the engine when pulling away from a dead stop in cold weather.
There is also semi-synthetic motor oil, which is a mix of synthetic base oil and mineral base oil. Many operators are experiencing successes similar to seasonal use of synthetics by going with this option.
With that said, there is no need to be concerned about compatibility of synthetic, mineral or semi-synthetic engine oil. As I’ve stated, you can often benefit by changing to synthetic or semi-synthetic oil in colder climates.
Just be sure you’re always using a quality product like Shell Rotella® motor oils to get the protection you need
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