Motor Oil Additives
By Larry Carley c2006
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Up to 25% of the liquid in a typical quart of oil is additive. Additives are what really make the oil and determine its performance properties. Additives extend the viscosity range of the oil, allow it to withstand high pressures and loads, handle contaminants in the crankcase, and reduce friction for improved fuel economy.
One of the most important additives is "Viscosity Index (VI) Improvers". These help the oil maintain a consistent viscosity as temperature and load change. "Pour point depressants" are also used to prevent the oil from thickening at low temperature for easier starting.
Modern motor oils also contain detergents and dispersants to reduce varnish and sludge formation to keep the engine clean. There are also "anti-oxidants" to minimize oil burning when the oil gets hot. This also helps reduce the formation of varnish and carbon deposits inside the engine.
Rust and corrosion inhibitors are added to counteract the harmful effects of water, unburned fuel and exhaust gases that blow past the rings and enter the crankcase. This prevents the formation of acids that can pit bearing surfaces. "Foam inhibitors" are used to minimize the formation of air bubbles as the oil is churned by moving parts. "Wetting agents" help the oil stick to hot surfaces so it doesn't run off and leave the metal unlubricated and unprotected.
Finally, there are "anti-wear" and "extreme-pressure" additives. These include zinc and phosphorus that provide wear protection when metal touches metal. Some racing oils typically have a higher dose of zinc to provide extra protection in high revving, high load applications.
AFTERMARKET OIL ADDITIVES & CRANKCASE TREATMENTS
Engine oil additives and treatments include friction reducers/modifiers, products that help reduce oil burning, engine flushes to remove carbon. varnish and sludge deposits inside the crankcase, and moly and teflon-based crankcase additives that help reduce wear and extend engine life. These products can't work miracles, but they can reduce oil consumption in older engines and help protect newer engines against premature wear.
Most vehicle manufacturers do NOT recommend using any type of aftermarket oil additive. Quality motor oils should contain all the additives that are necessary for normal service and to maintain oil lubricity between normal oil change intervals. On the other hand, most vehicle manufacturers do NOT prohibit the use of aftermarket oil additives in newer engines.
Aftermarket oil additives make the most sense for older, high mileage engines that are burning or leaking oil, or that may be used for severe service or racing.
In recent years, the level of phosphorus has been reduced in motor oil because phosphorus can contaminant the catalytic converter if the engine is burning oil. Phosphorus is an anti-wear additive, so there is some concern that lower levels of this essential additive may increase wear in older engines that have flat tappet cams instead of roller cams. To help protect older engines with flat tappet cams against wear, using an aftermarket oil additive that contains phosphorus or other anti-wear additives may help prolong engine life.
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