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The Truth About Synthetics: Way More Than Just Extra HP!

HOT ROD logo HOT ROD 1/3/2017 Hot Rod Network Staff
SONY DSC The Truth About Synthetics: Way More Than Just Extra HP!

Synthetic oil is nothing new, nor is the controversy about whether synthetic oil is better than mineral oil. The development of synthetic oils, derived from silicones and polyolefins, occurred in the United States in the early 1930s. Germany evolved the synthetic oil technology during WWII due to their lack of natural resources and a need for oil. The Germans developed synthetic hydrocarbons, polyglycols, and alklylbenzenes to support their war machine. The US furthered synthetic oil development in the 1950s and 1960s with research into fluorinated lubricants. In 1972, AMSOIL developed and marketed the first synthetic motor oil to meet the American Petroleum Institute (API) service requirements.

Oil is sorted in one of the five API base oil groups. Groups I, II, and III base oils are mineral oils that have been distilled and refined from a barrel of crude. Even after the refining, the hydrocarbon's molecular structural arrangement and sizing remain inconsistent, and the base oils contain organic compounds most notably, oxygen, sulfur, nitrogen, and certain metals. The varying shapes and sizes of molecules result in irregular lubrication surfaces, and these irregularities generate friction within the base oil, increasing engine power consumption and reducing performance. The remaining compounds in the base oil can lead to oxidation, acid development, and the creation of sludge, especially in high-temperature usages. Mineral oils have a viscosity index (VI) ranging from 80-120 depending upon its base oil group. The VI is an indicator of an oil's tendency to reduce flow with a rising temperature; higher numbers, associated with smaller changes in viscosity with temperatures, are desirable.

Groups IV and V base oils are synthetic oils developed via a process known as synthesizing. These synthetic oils have uniform-sized hydrocarbon molecules, and the base oils are free from contaminates and impurities resulting in a base oil that is consistent and durable. Synthetics have a VI in excess of 150. Group IV base oils are Poly-Alpha-Olefins (PAOs), and they have a wider temperature range compared to mineral based oils. PAOs work great in extreme cold conditions and high-heat usages. Group V base oils are classified as all other oils (esters), which includes silicone, polyaklylene glycol (PAG), polyol esters, etc. A common use of Group V base oils is to add the esters to another base oil. The addition of the esters improves the properties of the existing PAO base oil.

Synthetic oils have a wider temperature range of operation than do mineral oils. The pour point of a Polyalphaolefin (PAO) oil is outstanding, and this allows the oil to move to engine parts much quicker than mineral oil at low temperatures. Synthetic oils do have some extreme cold and hot concerns, but the limitations are well beyond the temperatures where mineral oils have already failed.© Hot Rod Network Staff Synthetic oils have a wider temperature range of operation than do mineral oils. The pour point of a Polyalphaolefin (PAO) oil is outstanding, and this allows the oil to move to engine parts much quicker than mineral oil at low temperatures. Synthetic oils do have some extreme cold and hot concerns, but the limitations are well beyond the temperatures where mineral oils have already failed.

PAOs formulated with esters tend to be the most popular for automotive applications. PAOs have an extremely high VI, high thermal oxidative stability (resistance to oxidation), low volatility (less oil loss at high temperature), excellent low-temperature viscosities, consistent base oil stock, excellent pour points, and have excellent hydrolytic stability (resist water) when compared to mineral oil. PAOs have some disadvantages, which include a limited ability to dissolve oil additives (solvency), a small chance to shrink seals, and higher consumer costs. To offset the disadvantages, adding diesters to PAOs increases the oil's solubility. Specific esters, called seal swell agents (SSAs) blended into the oil remove any chances of shrinking seals. SSAs are seal conditioners that clean the seal, and the PAOs lubricate the cleaned seal. Lastly, the higher costs of PAOs is offset by the extended service intervals of synthetic oils.

To improve the VI of an oil, enhancers called VI Improvers are added. The VI Improvers are long-chain molecules that can be fragmented by mechanical shearing, which in time results in a lower oil viscosity. Shearing occurs in high-stress areas such as the oil pump, crankshaft area, camshaft area, piston rings, etc. The oil (hydrodynamic film) can be briefly squeezed from between the two metal surfaces splitting the long-chain molecules into shorter, lower weight molecules. The shorter molecules offer less resistance to flow. Shearing can also contribute to deposits, causing sticking rings, increased consumption of oil, and increased engine wear. Synthetic oils often have the best VI Improvers and use less VI Improvers than mineral oils. Less VI Improvers help the oil maintain the higher-grade number (5W-20) for a longer interval. These VI Improvers maintain an oil film strength 5 to 10 times greater than mineral oils.

As mentioned earlier, one main advantage of synthetics is its robust boundary layer, which allows it to cling heartily to engine components when the engine is off. With vintage and high-performance automobiles, this can often be for lengthy periods of time. This protective boundary layer reduces the metal-to-metal contact during the critical seconds after engine startup. The excellent oiliness (a lower coefficient of friction of one oil compared to another fluid of the same viscosity) of synthetic oils reduces engine wear during the initial, critical engine startup. Mineral oils lack such a robust boundary layer, as the oil drains quickly to the oil pan when the engine is off. Nevertheless, the synthetic oil boundary layer affords an enthusiast the necessary piece of mind when their vehicle is started after an extended dormancy. By some estimates, initial start-up and running in the first seconds accounts for as much as 90 percent of all engine wear.

Prior to filling the transmission, a new factory filter and pan gasket were installed. Five quarts of AMSOIL's Signature Series ATF was tipped into the NAG1 transmission. The transmission was warmed up and a small amount of additional fluid was added. To accurately measure the required amount of fluid, a specialty tool and scan tool that provides the transmission temperature information are required.© Hot Rod Network Staff Prior to filling the transmission, a new factory filter and pan gasket were installed. Five quarts of AMSOIL's Signature Series ATF was tipped into the NAG1 transmission. The transmission was warmed up and a small amount of additional fluid was added. To accurately measure the required amount of fluid, a specialty tool and scan tool that provides the transmission temperature information are required.

Let's look at this in detail. The largest contributor to the superior shear load protection of synthetics is the uniformity of the molecules. In traditional mineral oils, the lube stock is refined from crude oil, such that all the molecules in the base stock have similar weights—they were sorted (i.e. "refined") by virtue of their boiling point. Structurally, however, these molecules can be quite different in shape and in length. The degree to which molecules are chemically similar is more a function of luck, and the geology of where the base stock originated.

By way of explanation, all base mineral oil stocks have a distillation curve that represents the average distribution of molecular weight, with the fat part of the curve—the oil's rated weight—being at the center of a Gaussian distribution (bell curve). Chemically, the compounds in such a diverse base stock will have different properties and shear strengths. In use, the smaller molecules at the bottom of the distillation curve will have a higher volatility and evaporate quickly, causing the oil stock to thicken over time. Longer chain molecules at the top of the distillation curve are mechanically weak and will break under severe pressure, reducing the effectiveness of the boundary lubrication layer. Since synthetic molecules are practically identical in length, structure, and shape, the Gaussian distribution of their weight is tight, so there is no practical variation in the strength or chemical property of constituent molecules. As such, this optimized oil stock shall protect far better, and for far longer than mineral-based oil stocks.

We contacted AMSOIL for a full array of synthetic oils for the engine, transmission, and rear end to test in our late-model Dodge. Our test vehicle would be a '06 5.7L Charger that had been using a 5W-20 oil, Mopar ATF+4, and Mopar 75W-140 (all mineral based oils). AMSOIL's Signature Series 5W-20 motor oil and matching EA synthetic media oil filter provide up to a 25,000-mile, 700-hour, or one-year service interval. The ATF chosen was AMSOIL's Signature Series Multi-Vehicle Synthetic, and the gear oil selected was AMSOIL's Severe Gear 75W-140 and a 4-ounce tube of AMSOIL Slip Lock additive.

With the AMSOIL products installed, the Charger burned five tanks of fuel to establish an estimate of fuel mileage. Our fuel mileage with the AMSOIL product increased by 0.9 mpg. The Charger was strapped to the Pennsylvania College of Technology's Mustang dyno, and the performance numbers were up as well. Peak torque was up 2.6 lb-ft and peak horsepower was up 4.4 hp. While we could not test component wear, AMSOIL and independent studies have shown the use of synthetics reduce wear and provide cleaner components leading to greater longevity of bearings, pistons, rings, clutches, bands, gears, etc.

So why not try synthetic oils in your Mopar? The initial cost is offset by extended service intervals and increased longevity of the engine components due to the uniform molecule structure, low-temperature pour points, superior stability of viscosity, better shear properties, and superior boundary layer protection. Protracted service intervals mean less disposal of waste oil, benefitting the environment. Finally, putting synthetics in your Mopar will benefit your wallet with better fuel economy, and you will have a few extra ponies under your right foot as a byproduct.

In spite of the immediate short-term benefit, the biggest advantage is in synthetic's ability to significantly prolong the life expectancy of critical wear components where metal-on-metal contact is greatest. If you plan on keeping your machine on the road for years well beyond the warranty period, a synthetic like AMSOIL will keep bearings, rings, bores, lifters, cam lobes, valve guides, bands, clutches, and pumps running like new well past normal rebuild intervals, and that means money in your pocket.

Got a vintage Mopar with flat-tappet lifters? The needs of older engines are significantly different than late-model engines with rollerized lifters. 

Related Video: How to Change Your Oil

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