Every engine manufactured will eventually wear out. Piston rings wear down and the engine will begin to burn oil, leading to smoke blowing out of the exhaust. Bearings wear thin, causing oil pressure to drop. Rods will wear out and begin moving around on their journals, creating noise and lowering oil pressure. Lifters will fail to hold pressure and begin making clacking noises. The common denominator is the wear leading to excessive parts clearances, and oil additives are often considered an answer.
Viscosity is basically a measurement of an oil's thickness. The usual measurements are two numbers separated by a “w” for multi-viscosity oils, and a single number for “straight” viscosity oils. The higher the numbers, the thicker the oil is. Oil additives often rely on the premise of increasing the viscosity of engine oil to help cushion the slack between worn operating parts. This is expected to help quiet the noise created by worn lifters and rods. This is considered a questionable premise by automotive experts because by this rationale, simply changing to thicker oil would have the same effect while supplying the engine with a fresh change of oil at the same time.
Many of the better known engine oil additive makers promote the additives contained in their products and claim various beneficial results are to be found by their addition to standard automotive oils. Most of the additives used in these products are the same additives already formulated into standard engine oils. Experts again have suggested that the same benefit can be had from a fresh oil change. Other products include unusual additives like PTFE to their products, but none has been proven to support the claimed benefits.
Numerous oil additive makers have advertised impressive results supporting their claims to reduce noise and prolong engine life. Independent tests dispute these claimed results. The Federal Trade Commission has ruled that several companies’ additive claims were unfounded, and numerous lawsuits have forced many of these additive companies to no longer make their claims of reduced wear or improved mileage. The FTC has ruled that many of the well known oil additive brands were engaging in deceptive and misleading advertising, and that scientific studies proving their claims would be necessary to settle any disputes. These studies have not been forthcoming.
Anecdotal or “word of mouth” evidence is often cited as support for an oil additive's effectiveness, but no credible study or testing has verified these claims. Numerous consumer testimonies have attributed improved mileage, prolonged engine life, and quieter engine operation with the addition of various oil additives. These testimonies are usually provided by the makers of the products, making bias a concern, as well as the poorly documented nature of the claims. Without authoritative support to validate them, the anecdotal testimonies lack credibility.
Several studies examining the effectiveness of oil additives have been performed. There are currently no credible studies to support any claims that these additives will improve mileage, or prolong engine life. Studies performed or commissioned by federal agencies have concluded that these additives are ineffective and do not support their claimed abilities. Independent studies and tests have reached similar conclusions, and refute the claims made by the makers of the products.
