Auto Service World
Feature   May 1, 2001   by Jim Anderton

Test tube lube

Synthetic engine oils have been around long enough to develop both myths and legends


“You can’t use it on older engines. It has superior lubricating properties to mineral-based oils. It’s really the same as conventional engine oils. Once you start using it, you can’t go back.” An incredible number of myths have surfaced surrounding synthetic engine lubes, and many persist in the face of plenty of evidence to the contrary.

Just what is synthetic oil?

In a sense, all engine oils are “synthetic” in that they’re in a form that’s far from the black stuff that’s pumped out of an oil well. In this case, “synthetic” refers to the lubricant’s base stock, which is petroleum-derived in conventional oils, and is manufactured for synthetics. Clinton Smith, technical services specialist, engine oils for Imperial Oil Products and Chemicals Division describes the key benefits of synthetics: “There basically are two. All additives in any engine oils are synthetic, so even conventional oils contain synthetic materials. The normal synthetic base stock is poly alpha olefin, or PAO; it has a couple of advantages. One is that it’s wax free. Oils made from crude oil have wax in them, which must be dewaxed”. The dewaxing process isn’t perfect, however, forcing the use of other additives such as pour point depressants to compensate, says Smith. “In general synthetics have better pour points and better pumpability as well. The other area is oxidation stability. If you look at the molecular character of a normal base stock, you’ll see thousands of structures. For PAO, it’s more like ten to twenty. We’ve eliminated many of the types that would be oxidatively unstable. The consumer sees this as oil that darkens slower than a mineral oil and as viscosity that will increase at a much slower rate than mineral oil. It gives better protection to the engine, and it will keep the engine cleaner.”

Jim Arner, technical services manager for Texaco Lubricants Company agrees: “the portion of the crude oil separated (by distillation) to make motor oil can still be a broad mixture of molecular shapes and sizes. Refining technologies are very good these days but you are still limited in the overall performance of this conventional base oil. In comparison, because you can define the shape and size of the synthetic molecule created, you can obtain better fluid characteristics such as reduced oil volatility, improved low temperature fluidity, and better oxidation stability. In other words, with synthetic oil you’ve essentially kicked out the weakest link. It’s actually more complicated than suggested here, but the important part to remember is that a synthetic molecule can be carefully crafted at the refinery to produce the desired characteristics, whereas with a mineral oil base you may have to compromise on some performance characteristics. Add to that the added performance provided through the additive technology and you end up with excellent performance provided by today’s synthetic motor oils.”

Reading labels

Consumers get much of their product knowledge regarding engine oils from the media and from those plastic bottles racked at he self-serve pump. The API (American Petroleum Institute) “donut” containing the API service code and SAE viscosity rating is the seal of approval for many drivers, and a few are knowledgeable about the API “starburst” signifying compliance with current standards of the International Lubricant Standardization and Approval Committee (ILSAC), a joint effort of both American and Japanese auto manufacturers. “SJ” is he current API standard, but ILSAC has a less well known specification, GF-2, which is important because of the need to preserve vehicle emission control systems. A key component of many oil additive packages is phosphorus, which in sufficient quantity can “poison” catalytic converters. GF-2 limits he amount of phosphorus to 0.10 percent, and addresses another issue important to emissions: volatility. Remember the distillation process used at the refinery? Engines act as a sort of refinery too, vaporizing the lighter fractions and burning them in the combustion chambers by way of the PCV system. The extra hydrocarbons must be dealt with by the catalytic converter, so the less the oil contributes, the easier emissions can be controlled. Synthetics have a much narrower distribution of “molecular weights”, resulting in oil that can more easily meet GF-2 standards. Another issue within GF-2 is the presence of a Chrysler-derived turbocharger high-temperature deposit test. Turbochargers heat soak significantly after engine shutdown, potentially coking the oil stationary in the turbo’s bearings. Synthetics’ excellent high-temperature stability makes then a good approach to turbocharger coking.

Complicating the issue even more is the move toward a tougher GF-3 standard. GF-3 demands improvements in high temperature deposit formation, oil aeration (foaming), and oil consumption, requiring low volatility base stocks with a high viscosity index and a narrow boiling range. Varnish, sludge, corrosion, oxidation and wear limits are similar to GF-2 / API SJ standards. GF-3 will be good for the environment and motoring public, but more standards will likely result in consumer confusion, especially given the proliferation of multigrade viscosities, and the absence of strong European representation in ILSAC, meaning different standards from European carmakers. Inject synthetics into this mix, and consumers are vulnerable to misinformation and rumor.

Telling an urban commuter that their stop and go driving represents “severe service” is likely to generate some disbelief, but there is a good argument that all Canadian driving is severe. An approach to converting consumers to the benefits of synthetics is to attack the source of the confusion, says Kara Zavitz, consumer marketing manager for Castrol North America: “The hurdle that the consumer needs to clear, and that the technician needs to communicate, is that by using a synthetic product, the consumer doesn’t have the stress or concern about whether their vehicle and driving pattern fits the norm for recommended driving conditions. Synthetics are more stable and can deliver a broader set of driving conditions. It’s definitely worth the extra money.”

Synthetics are excellent, but it’s important to note that quality, approved mineral oils are completely adequate for most drivers and vehicles. It’s too early to tell if toughening automaker requirements will force an expansion of synthetics into mainstream OE vehicles, but approved synthetics are a premium aftermarket option for consumers who love their cars, or drive under difficult conditions. And in Canada, that makes essentially every vehicle a possible application. SSGM


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