Performance & Hotrod Business May '14

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82 n Performance & Hotrod Business n May 2014 The second test is simply: "Will it pump?" Some oils will flow at one temperature but cannot be pumped at that temperature. Once the two tests are completed and com- pared, the "winter" number is established. The higher number is from the rate of flow at 100 degrees centigrade. Since all oils thin out and heat causes them to lose vis- cosity, straight weight oils have limitations. The difference in viscosities for most single grades is too large between the extremes of temperature in engines so multi-grade oils became the norm. Viscosity Okay, there is that word "viscosity." Just what is it? Answer: it is the resistance to flow. Estab- lishing oil that will resist thinning requires viscosity index improvers (VII) such as poly- mers. Polymers (and similar materials) in- crease the viscosity without making the oil thicker. No oil with VIIs can be rated as a single grade or "straight weight." This is a good time to understand that oils have two purposes in internal combustion engines: 1) lubrication and 2) cooling. Se- lecting the right oil will depend on the ad- ditives in it. Most oils are 80-percent base oil and 20-percent additives. The different additive packages determine the characteristics of the oil. The best rule is to use what the manufac- turer recommends. Only when the engine is modified does this not apply. It is important on modified, or high-performance engines, that the oil selected meets the requirements of the application. Examples: An engine used in drag racing might only reach 100 degrees in tempera- ture, while a Sprint car engine must live at 300 degrees. One oil will not be efficient for both. A 500-hp short track engine will not have the same pressure on the rod bearings as a 2,000-hp turbo Mustang, so different additives are necessary. Other factors can result in the need for other ad- ditives, like friction modifiers or anti-cor- rosion chemicals. Most of the specialty oils available are not API-rated and do not meet modern catalytic converter requirements, but do provide "the right oil for the application." Today's API rated "SN" oils are not right for pre-1995 engines or any high-performance engine, in spite of some manufacturers' market- ing claims. The detergents in "SN" oils are stronger than ever before and are able to keep the metals protected from dirt and other foreign elements. Unfortunately, they do not know "zinc" from dirt. More on that subject in Part Three. What Is Zinc? Zinc is a basic element/metal that has very little to do with what we use in our engines. Zinc is the primary ingredient for "galvanizing." The zinc in engine oils is either ZDP or ZDDP. We call it "zinc" to keep from hav- ing to learn the long word(s). It would be more correct to refer to it as a phosphate, because phosphorous is the main/key ingre- dient. Putting ZDDP under heat and pressure forms a glass phosphate film that becomes the barrier between metals. "Zinc" is not a single chemical, but a group of chemicals. There are over 50 different formulas for zinc. To understand why there are so many, let's use an oversimplified example of some ZDDPs. One is referred to as "fast-burn." For lack of a better explanation, it is soft and easily squeezed into the porous surfaces of newly machined parts and gives good, fast break-in results—but is not long-lasting. It is used in break-in oils and, after break-in, is replaced with oil containing a slow-burn, harder, long-lasting ZDDP for durability. Each formula of zinc is different and designed for specific applications. The lat- est zinc additives (since 2011) are designed to create less oil vapor. This "phosphorous the truth about oil PHBMAYp58-91.indd 82 4/2/14 2:06 PM

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