Group IIIs are a somewhat controversial class as they are derived from crude oil like Groups I & II, but their molecules have been so changed by severe processing that they are marketed as Synthetics. Most people now accept Group IIIs as synthetic, but the discussion remains heated among purists, and I’m going to duck by not taking a side here.
Synthetic base oils are manufactured by man from relatively pure and simple chemical building blocks, which are then reacted together or synthesized into new, larger molecules. The resulting synthetic basestock consists only of the preselected molecules and has no undesirable weak links that inhibit performance. This ability to preselect or design specific ideal molecules tailored for a given job, and then create those molecules and only those molecules, opens a whole new world for making superior basestocks for lubricants. In fact, the entire formulation approach is different: instead of trying to clean up a naturally occurring chemical soup to acceptable levels with a constant eye on cost, the synthetic chemist is able to focus on optimum performance in a specific application with the knowledge that he can build the necessary molecules to achieve it. And since full synthetic oils are generally a company’s premier offering, their best foot forward so to speak, the additives are often better and in higher doses as performance trumps cost.
In general, synthetic base oils offer higher oxidative and thermal stability, lower pour points, lower volatility, higher VI, higher flash points, higher lubricity, better fuel economy, and better engine cleanliness. The amount and balance of these improvements vary by synthetic type, and can be quite significant for the engine and user.
There are many types of synthetic base oils, the most common being Polyalphaolefins (PAOs), Esters, Alkylated Naphthenes (ANs), and more recently Group IIIs. These different types of synthetic base oils are often blended together (or even with mineral oils), to give the balance of properties desired. All offer improved performance, but at a higher price, which brings up the question of value – how much performance to you need, and how much should you pay for it?
For the average car owner, driving conditions are mild enough for conventional mineral oils to work satisfactorily, provided they are changed relatively frequently (3,000-5,000 miles). For those users with high performance engines, severe climates, hard driving, or utilizing long drain intervals, synthetics can offer good value and may even be required. And then there are those who so love their cars that nothing but the very best will do for their baby.
So, as you can see, modern motor oils are very simple mixtures of very complex ingredients. Choosing the right components of the right chemistry in the right dosages is a real balancing act, as each of the components have their own pluses and minuses and can interact or compete with each other. Don’t try this at home – leave it to companies you trust who have the technology, R&D, and resources to achieve the necessary balance so critical to performance.
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