Isn't Synthetic the same as Fully Synthetic (just a different name)
Mineral or synthetic?
Mineral oils are based on oil that comes from dear old Mother Earth which has been refined. Synthetic oils are entirely concocted by chemists wearing white lab coats in oil company laboratories. For more info, see the section on synthetics further down the page. The only other type is semi-synthetic, sometimes called premium, which is a blend of the two. It is safe to mix the different types, but it's wiser to switch completely to a new type rather than mixing.
They only mention mixing Mineral and Synthetics - which basically gives a semi-synthetic
I'm sure there is someone else on here who could clarify though??