Mixing synthetic oil and conventional oil

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Rank V

Advocate III

Smith Mt. Lake, VA
Member #


I'll also jump on the Mobil 1 bandwagon!

It is specified for our Porsche and I've used it in all our gas engines.

I run Shell Rotella T6 5W-40 in the Jeep EcoDiesel and my F-350 diesel as well as our construction equipment and have never had an issue in over 30 years...


Rank I

Traveler II

Cashmere QLD 4500 Australia
Member #


Another issue you need to be aware of is that modern engine oil is not just oil - oils use many and varied additives to achieve specific ends. Detergents are used to remove contaminants from engine components but there are many other additives that help maintain viscosity over the life of the oil, and yet others that help the oil deal with extreme heat and/or cold and lots of other things.

When you mix different brands of oil or even different types of oil from the same manufacturer you risk the various additives working against each other and the oil delivering less than optimal protection.

The science behind modern lubes is almost "rocket science" and unless you really know what you are doing I think it's better to follow the expert's recommendations.