Oil Additives – What are They and Does My Car Need Them?

Among mechanics and automobile enthusiasts, there has always been controversy about oil additives. Some drivers claim that oil additives are unnecessary hype, while other drivers would not drive without them. Those who use these additives claim higher fuel mileage, reduced engine noise, and longer times between service intervals. Each driver needs to consider the benefits of using these additives and decide if they are worth it. Following is a discussion of several types of oil additives found both in motor oil and as an aftermarket supplement.

Corrosion and Rust Inhibitors

These additives neutralize the acid in motor oil and slow rust, or oxidation, in your engine by repelling water on engine components. The engine’s internal parts receive protection when the additives lay a thin film on top of these parts and protect them. There may not be just one corrosion and/or rust inhibitor in these additives, because most oils have several.

Anti – Wear Additives

These additives protect engine parts from normal wear and tear. They are heat activated and react with the metal in your engine. Like corrosion and rust inhibitors, they coat the surface and improve engine lubrication. These additives can prevent engine seizure by reducing friction and preventing corrosion and slowing oxidation. But these additives can increase emissions and shorten the life of the catalytic converter. Some products offer a zinc replacement additive that lubricates your engine but reduces emissions. This protects your catalytic converter.

Viscosity Modifiers

The viscosity of your engine oil shows how easily oil moves at a certain temperature. Thick oil has a higher viscosity while thin oil has a lower viscosity; so, thin oil pours more easily in colder weather than thicker oils do. When you are purchasing oil, the viscosity advertised on the can is tested at 100°C and describes the resistance to the oil thinning with greater temperatures. This information can help your car during temperature extremes. For instance, during cold weather your car’s engine needs oil that has low winter viscosity. When you are shopping for oil, you will see oils such as 10W and 5W in the oil description. The number following this shows the viscosity. Instead of using an aftermarket additive, one can find the oil viscosity they need already built in to the oil. For example, 0W-20 and 5W30 viscosity oils are for cold climates and 15W-40 or 20W-50 oils are for hot climates.


These additives remove deposits and prevent rust from engine parts. Similar to laundry detergent, engine detergents keep the engine clean and free of impurities and dirt. Because detergents keep impurities soluble, they are important to keep oil sludge from forming in your vehicle’s engine.


These additives help to disperse the contaminants in the oil so the engine is not damaged. Dispersants delay formation of sludge, varnish, and acid on an engine’s interior, which can clog the engine if left unattended. Dispersants and detergents are common additives found in engine oil, with the goal being to suspend contaminants. This suspension keeps the contaminants off the wall of the engine and allows the contaminants to flow out when the engine oil is changed.

Is an Oil Additive Necessary for My Car?

You may wonder why you need an oil additive if these additives are already in your engine oil. Considerations include high mileage vehicles, older vehicles, or vehicles that are showing signs of wear. If you hear strange noises, smell unusual odors, see steam or smoke, or see your check engine light, your engine may be old and worn. Vehicles with engines that show the signs of wear and tear may need engine oil additives to improve lubrication, slow oxidation, and/or reduce friction. The driver should watch their gas mileage, because a reduction in gas mileage can signal your engine’s improper function. In addition, you can just sit and let your engine idle, to see if it runs roughly or misses.

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About the author: Wifred Murray

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