My Mustang uses 100% synthetic oil.........................
Synthetic oils are typically created from chemically modified materials such as petroleum components, but the base material is almost always distilled crude oil. Any additional additives and the actual synthesis process for creating synthetic oil varies among producers and is considered a trade secret.
“Sythetic” comes merely from how the base crude is modified (as opposed to simply more “refined”) and added to with various chemicals.
The base is still a fossil fuel (crude oil).