Synthetic oils: Real need or marketing hype?

Even though synthetic motor oils have been with us for more than 30 years, they have only recently become highly visible. During the last five years, all major motor oil companies have introduced a synthetic motor oil, and many have added a partial synthetic product to their line. Considering the fact that most of these oils are significantly more expensive than conventional mineral-based motor oils, you need to be sure that you and your customer are actually receiving additional performance for the extra money. But how can you tell? The following information will help you decide for yourself.

First, it is important to know that the development of synthetic motor oils (and synthetic lubricants in general) was based on real needs. Much of the early synthetic motor oil development work was driven by specific military needs that became evident during and immediately after the second world war. Frozen motor oil and gear lubricants proved to be disastrous in arctic battlefield conditions. It was lubricant thickening as much as partisan resistance that stopped German tanks at the gates of Leningrad during the bitter winter of '41. On the other side of the world, thickened oil resulting from extremely hot engine operations, desert heat and sand brought Rommel to a near standstill more than once. But it wasn't until the commercial development of Alaska's north slope and other ventures above the arctic circle that the development of modern synthetic motor oils began in earnest.

While these examples are a bit dramatic, they do serve to illustrate a simple fact. Synthetic oils are designed for and should be used in severe driving conditions. Under most ordinary driving conditions, conventional motor oils are recommended and work just fine. Some notable exceptions are

• driving in extreme heat for long periods, particularly if towing or hauling heavy loads. In the southern U.S., scorching summer temperatures can place unusual stress on engine oils. Synthetic oils effectively combat the damaging effects of excessive heat because of their high resistance to oxidation.
• operating vehicles in areas where the temperature averages 10 Fahrenheit, particularly if you do a lot of stop-and-go, short trip driving. The bitterly cold winters in the northern U.S. are a prime example of where synthetic motor oil could provide exceptional value. Their inherent low temperature fluidity can provide thicker oil flow and easier starting at these icy temperatures.

In addition to severity of driving conditions, maintenance routines should be considered when choosing between conventional and synthetic motor oils. If your customers' maintenance habits are erratic and they tend to exceed manufacturers' recommended drain intervals, our experience teaches that synthetic oils are somewhat more forgiving. Do not, however, think of using synthetic oils as a safe way to exceed recommended drain intervals. One of motor oil's primary functions is to keep combustion debris, dirt and dust in suspension. In this regard synthetic and mineral oils are no different. Also, by extending drain intervals, your customers are probably extending oil filter service. Filters get equally dirty regardless of the oil used. In time, all filters become saturated with debris, after which they will no longer function effectively and will not remove additional contaminants from the oil.

Synthetics should also be used when they are recommended by the OEM (original equipment manufacturer). Currently, the only OEM specification that suggests the use of synthetics is GM 4718M, which was written specifically for the Corvette LT1. This recommendation is based more on what isn't under the hood than what is, namely an oil cooler. Owing to limited cooling capabilities and very confining engine departments, engines like the LT1 typically carry an oil cooler which keeps engine oil operating temperature within normal ranges (below 240 F). An oil cooler is absent from the LT1.

Now that you know that synthetic motor oils are useful in specific, severe service applications, you don't have to think too long about part-synthetic oils to realize that they are largely driven by marketing opportunity and do not have a significant role in modern lubrication. These oils, often referred to as "synthetic blends" or "semi-synthetic oils," typically contain between 15 and 30% synthetic base oil and at best give a conventional oil approximately the same percentage of "synthetic character." With applications for genuine 100% synthetic oils limited, and with conventional and synthetic oils identical in so many performance areas, it is hard to imagine a legitimate application that would recommend use of a part-synthetic.

Our overall recommendation is to stick with conventional oils unless you have an application similar to those described above. If you need or just want to use a synthetic oil, make sure it meets the latest API specification, currently SH. After that, your best bet is to stick with a name brand and get the best deal you can. We are unable to find an application for part-synthetics and advise that if you have any doubt, buy a 100% synthetic.