Oil Bay: Is it Wise Synthesize?
Oil Bay
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Is it Wise to Synthesize?
In a bid to extend drain intervals and improve fuel economy, synthetic engine oils may be part of the solution.
by John G. Smith, Contributing Editor
s slick as it might appear, a mineral-based engine oil offers some pretty rough terrain at a microscopic level. The different lengths and sizes of its molecular chains tend to look downright jagged when compared to the uniform spheres that would be seen when peering deep into the depths of a synthetic oil. “There’s no wax, there are no impurities, and the molecular structure is extremely uniform [in the synthetic offering],” observes Yeong Kwon, product offer advisor for commercial vehicle lubricants at ExxonMobil. The differences are not only skin deep. The chemical make-up of a synthetic formula allows it to resist oxidation, making the oil an attractive option for those who need a longer-lasting fluid to support extendeddrain intervals, or for those who are pushing engines at high temperatures and high loads over an extended period of time. The oils also pump more freely in cold temperatures and basically offer measurably better viscosity at extreme temperatures of any sort. But it is the promise of fuel economy improvements that may be capturing the imagination of a wider group of users. Suppliers tend to refer to potential fuel economy gains of at least 1 percent thanks to the reduced friction, and the performance is even better when coupled with synthetic gear oil. That can be welcome news for fleets that are trying to reclaim some of the fuel economy which was lost with the onset of exhaust-cleaning equipment mandated by the U.S. Environmental Protection Agency. Shell, for example, reported a fuel economy gain of 1.6 percent after running six test trucks around a track to measure the impact of various options. And last November, Valvoline introduced its “fuel proof” guarantee that promised a positive return on the investment, even after factoring in the higher price of the synthetic lubricants.
VISCOSITY VARIABLES The gains are largely realized with the combination of the right viscosity to protect engine components, and a low viscosity that makes the oil easy to pump and minimizes pumping losses. “In most cases, synthetics are a lower viscosity product,” notes Dan Arcy, OEM technical manager for Shell. “If you were to make a 15-40 synthetic, you wouldn’t really be getting any advantage of low-temperature [properties]. The benefit comes from making the wider viscosity range.” Instead of using a 15W-40, the grade that currently dominates the trucking market, the availability of synthetics can move a truck owner to a 5W-40, which pumps more freely at lower temperatures. That leads to easier starts at
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