All Synthetics Are NOT Created Equal

In the past, it was always believed that purchasing a synthetic oil meant just that, you were buying an oil that was man made rather than a petroleum that was pumped out of the ground. Towards the end of the 1990s this all changed with the reformulation of Castrol Syntec. They had changed their formula from a PAO base stock, which was one of the most commonly used base stocks at the time, to a petroleum base that had gone through a process called Hydrocracking. This process refines the oil very well, to a point that Castrol called it a Synthetic. While doing some testing Mobil discovered the formula change and took Castrol to court claiming that they were false advertising the oil as a Synthetic, since it's base stock was made from a petroleum. Mobil's stand basically said that a "synthetic" oil is something man made in a lab to certain specification that cannot be found in nature that way, which was the common thought even consumers had at the time. Castrol's stand was that this process the oil went through was so refined that it no longer resembled anything in nature, therefore it was a "synthetic." Because the API couldn't come up with a good definition of a synthetic themselves, they accepted Castrol's definition.

This type of oil was less costly to produce than the PAO based synthetics (although it has been effected by the rising petroleum costs of the past few years). Unfortunately the consumer never benefited from the lower manufacturing costs, and it seems the oil manufacturers most likely made a bigger profit from each sale. This has now changed how oil is made and sold, and it's classification. There are five Groups of oils. Group I rarely is used anymore, while Group II is your common petroleum oil. This "hydrocracked" oil is commonly referred to as a Group III oil, while the PAO synthetics are a Group IV. Group V oils do exist, but are uncommon, and typically not often used for automotive use.

From the information given to me last, EVERY synthetic on the market today has converted over to this Group III oil, with the exception of most of the Amsoil line, Mobil 1, and a few other specialty oils, usually more difficult to find. Amsoil's XL line of oil is a Group III oil. It is not designed for the extended drains that their other lines are, therefore, the Group III formula is perfect for it's recommended drain interval. When this oil became a Group III oil, Amsoil did lower their price, unlike the competition. Amsoil's standard 25,000 mile oil and their Series 2000 is a Group IV "Genuine PAO Formulated Synthetic" oil.

Yet there are differences between the Group III oil qualities as well. Many manufacturers purchase a base stock that is refined just enough to push it out of a Group II classification and into the Group III where they can call it a synthetic and charge the higher price. In many cases, these oils are not much better than a quality Group II oil. In the case of the Amsoil XL oils, Amsoil purchases the highest quality Group III base stock available. This is one of the reasons it performs so well.

Group III oils have been around for a few years now, and are being used in other applications as well, such as Transmission Fluids and Gear Lubes, however, as time continues, it is being found and noted that they do not last as well as the PAO Synthetics. And this seems logical, it is still a Petroleum based oil, and suffers the same breakdown temps as the less refined Group II oils. For this reason, these fluids are being beefed up with additives. But rather than slowly breaking down over time, like the Group IV fluids, these fluids tend to remain stable until the additives wear out and rapidly drop in their performance and protection. For this reason, many vehicle manufacturers who were putting a synthetic into their products for the added protection, are finding that they are not getting what they expected, and it is predicted that many future Owner's Manuals will stop requiring merely a "synthetic" oil, but specify a Group IV synthetic.

Below are some comparisons of oils you might now even be using. This data was compiled in the Spring of 2003 by Amsoil Dealer George Kimball. Note how each rates, the "base" the oil really is, and the cost comparison of using a superior product: Amsoil!

COMMON 5W-30 SYNTHETIC OILS*

COMMON 10W-30 SYNTHETIC OILS*