Any time we get something in the final product that we don't want, we call it an impurity. In oils we may have compounds that we refer to as aromatics as well as some other things that get into the base oil. How well these aromatics are filtered out determines what grade of base stock we have in motor oil. Group I oils have the most contaminants. Up to 10% of the total base stock! Group II oils have a little more distillation (refining) done to bring these contaminants down somewhat. Up to this point we all still agree that we have conventional "dino" oil.

A Group III oil will take the refining process one step farther through a process called hydrocracking. This is whee we go back to the chemistry equation balancing act from above. Through the introduction of hydrogen (hence the "hydro" in hydrocracking)into the mix under high temperatures and pressures, the hydrogen molecules add themselves to the aromatics (contaminants) to completely change their molecular structure into somethig else. The end result is naphtenes and alkines. A chain of napthenes is called paraffins but through the hydrocracking process the aromatics are gone. This is a good thing. Through a simple chemistry formula balancing act in the real world we have taken something we didn't want and rearranged it with some outside help into something we did want. This process is not naturally occurring and therefore "synthetic". This is what makes a synthetic what it is. It may still be from a "dino" based oil. The end product is still something natural. It was the way we got it that wasn't.

Now to move on to the Group IV and V synthetic oils. Their base stocks are different. Sort of. Group IV base stocks are called Poly Alpha Olefins. Remember how I mentioned alkenes above? An Alpha Olefin is an alkene where the carbon-carbon double bond is between the #1 and #2 carbons in the molecule. Again, it's just a process to create this but the original product was all natural! A poly-alpha-olefin takes this one step farther and is nothing mroe than a polymer made by polymerizing an alpha olefin. This is a Group IV base stock. It was a base stock that made an natural end product through unnatural processes. Group V oils may use different substances as a base stock but still arive towards the same end result which is something natural through an unnatural process.

Now just to throw a little bit of conspiracy into things let get into a human equivalent of the synthetic oil. Lets say a woman wants to have a baby but for some reason the husband's troops are awol. They decide to use artifical insemination. A doctor goes in and fertilizes the egg in a way that is not natural (or fun!). 9 months later they have a baby. Do we consider the baby a synthetic human? Nope. We consider the conception artifical but we don't call the final product artifical. Synthetic oils are a process but the end result is all natural. Their advantages are that we can go in and get rid of or convert what we don't want into something better. In regards to the baby comparison just think of it as gene manipulation to create a smarter human. The bad sides of synthetics have been during the formulation stages early on where some compounds were allowed to exist that didn't do rubber parts any good. This was easily taken care of. The carbon buildup issues have nothing to do with the base stock but rather with what is added to it by each oil manufacturer. This is the additive package.