Generally speaking, synthetic motor oil will nearly always last longer than conventional oil, saving you time and money. But your specific synthetic oil change interval will depend on several factors, including operating conditions, motor oil quality and personal preference.
Why Does Oil Lose its Effectiveness?
Extreme heat hastens chemical breakdown (oxidation), altering the oil’s chemistry and preventing it from lubricating, cooling and protecting as designed. Sludge can form, which clogs narrow oil passages and prevents oil from reaching vital components, causing wear. Oxidation can also lead to increased oil viscosity, which negatively affects energy efficiency. Ultimately, the oil loses its effectiveness and must be changed.
Contaminant build-up also affects oil life. Motor oil is formulated with detergent and dispersant additives responsible for holding dirt, soot (in diesel engines) and other contaminants in suspension and preventing them from depositing on engine surfaces or forming sludge. These additives are sacrificial in nature, meaning once they’re depleted, the oil’s effectiveness suffers and it must be changed.
Better Raw Materials Equal Better Oil
Like any other product, quality plays a big role, and in the case of motor oil helps determine service life and effectiveness. Synthetic motor oil is formulated using higher-quality raw materials than conventional oil, allowing it to perform better and last longer.
AMSOIL Signature Series Synthetic Motor Oil, for example, is guaranteed for 25,000 miles/700 hours of operation/one year, whichever comes first, in normal service (15,000 miles in severe service). Its synthetic base oils don’t contain the impurities inherent to conventional oils, allowing it to more effectively resist chemical breakdown and extreme heat. Signature Series is also formulated with high-quality additives that effectively neutralize contaminants for long service life.
The graph helps demonstrate this fact. A key indicator of potential service life is the oil’s Total Base Number (TBN), which indicates the oil’s ability to neutralize contaminants, such as combustion by-products and acidic materials. Higher TBN oils are able to neutralize a greater amount of acidic materials, which results in improved protection against corrosive reactions and longer life.
Compared to nine leading synthetic oils, Signature Series ranked first in the TBN test. It delivers a combination of long service life and outstanding protection other oils simply can’t touch, helping you get the most out of your vehicle and save time and money. In fact, no other oil available offers a drain interval of up to 25,000 miles.
AMSOIL also formulates XL Synthetic Motor Oil (10,000 miles/six months, or longer when recommended in owner’s manuals or indicated by electronic oil life monitoring systems) and OE Synthetic Motor Oil (3,000+ miles/3+ months), providing three tiers of AMSOIL performance.
Note: These test results describe and represent properties of oils that were acquired November-December 2012. Results do not apply to any subsequent reformulations of such oils or to new oils introduced after completion of testing. All oils were available to consumers at the time of purchase. Testing was completed February 2013 by an independent, third-party lab. Formulations were coded to eliminate bias, and samples were tested in random order. An appropriate number of trials of each oil were run to produce results at the 95 percent confidence level when compared to AMSOIL Signature Series Synthetic Motor Oil.