Like just about everything else, motor oil has a lifespan. Even the best oils eventually require you to change them. Historically, many motorists like the convenience of changing oil with the seasons, visiting the quick lube or pulling the ramps out of their garage each spring and fall.

Motor oil can deteriorate by becoming contaminated, the additives depleting over time or both.

How oil becomes contaminated

Base oils are the backbone of the finished lubricant that ends up in your engine. They can be conventional, synthetic or a combination thereof. They’re responsible for lubricating components, which reduces friction and protects against wear.

Base oils can lose their effectiveness over time due to a few different factors.

Oxidation – The interaction between oxygen molecules and motor oil molecules naturally leads to chemical breakdown. Just as oxygen causes a cut apple to brown or exposed metal to rust, it breaks down base oils and reduces motor oil’s effectiveness. Oxidation can lead to increased oil viscosity, which negatively affects energy efficiency. It also causes the formation of harmful deposits and sludge.

High heat – Today’s engines run hotter than ever before, with temperatures up to 235°F, and even higher if towing or hauling. The rate of oxidation for oil doubles for every 18°F increase in temperature.

Moisture – Your vehicle is also subjected to temperature swings, even when it is parked in the garage. Those temperature swings cause condensation to form inside your engine, leading to water contamination. Leaving a vehicle parked for extended periods or taking short trips that don’t allow the engine to fully warm up allow water to remain in the oil rather than evaporating and exiting through the tailpipe. Water can lead to formation of sludge.

Viscosity loss – A lubricant’s viscosity is its most important property. Viscosity has a direct bearing on wear protection, and your engine is designed to operate best using a motor oil of a specific viscosity (e.g. 5W-30). The intense pressure the oil bears as it’s squeezed between moving parts, like the piston ring/cylinder wall interface, can tear apart, or shear, its molecular structure, leading to viscosity loss. Suddenly, the 5W-30 motor oil your engine was designed to use is now essentially a 5W-20 oil, and wear protection may be compromised.

Fuel dilution – Fuel can wash past the piston rings and contaminate the motor oil, causing it to lose viscosity. Frequent short trips that don’t allow the oil to reach normal operating temperature can be especially problematic because the fuel won’t volatilize and exit through the PCV system. Excessive fuel dilution leads to sludge and varnish, requiring the oil to be changed more often.

Additive are designed to deplete

Additives are added to base oils to reduce destructive processes and enhance beneficial properties. For example, antioxidant additives help slow the rate of oxidation. Detergency additives help prevent deposits and sludge while cleaning pre-existing deposits. Anti-wear additives are added to some lubricants to form a sacrificial barrier on metal components and help prevent wear.

Since they’re sacrificial in nature, additive depletion is one of the primary reasons motor oil loses its effectiveness and must be changed.

Though all motor oils eventually deteriorate, synthetic oils last longer than conventional oils and deliver improved protection against wear and deposits. They’re formulated with base oils that are more resilient to oxidation and heat, while their additives also typically offer improved performance.

In fact, AMSOIL Signature Series Synthetic Motor Oil performs so well you can go up to 25,000 miles/one year between oil changes (15,000 miles/one year in severe service) if you want, saving money.

AAA Study Finds Synthetics a SIGNIFICANTLY Better Alternative than Conventional

AAA Testing Affirms Superiority of Synthetic Motor Oils

AMSOIL introduced the world to synthetic motor oil in 1972, and we’ve been extolling the benefits ever since. While we’ve been joined by many vehicle and equipment manufacturers and competing motor oil companies over the years, the American Automobile Association (AAA) is the most recent company to promote the benefits of using synthetics. The popular club recently conducted in-depth testing to determine if it’s worth paying more for synthetic oil over conventional oil.

The answer is a resounding “yes.”

“Oil protects critical engine components from damage and AAA found that synthetic engine oils performed an average of 47 percent better than conventional oils in a variety of industry-standard tests,” said John Nielsen, AAA’s managing director of Automotive Engineering and Repair. “With its superior resistance to deterioration, AAA’s findings indicate that synthetic oil is particularly beneficial to newer vehicles with turbo-charged engines and for vehicles that frequently drive in stop-and-go traffic, tow heavy loads or operate in extreme hot or cold conditions.”

AAA’s research included eight industry-standard ASTM tests focusing on shear stability, deposit formation, volatility, cold-temperature pumpability, oxidation resistance and oxidation-induced rheological changes. Each test was performed on five synthetic and five conventional oils. The results of this study by a reputable, third-party organization reaffirm what we’ve been saying for more than 45 years and give you one more reference point to back up your claims in the buy-sell process.

Click here to see the full AAA report.

Gone is the adage, “As long as you change your oil at 3000 mile intervals, I don’t care what oil you use, it will be just fine. Synthetics are a waste of money.”

The above ignores many issues which this test and AMSOIL has outlined for decades. Not only that but it totally ignores the #1 reason for our brand which is performance.
An unscientific approach can also explain. If you imaging all the cars in the junkyard that are there because of an engine that failed I bet the majority of them did get their oil changed at 3000 miles. At least that is true if we go back to the 70’s. So changing oil too frequently didn’t prevent a seized engine due to loss of coolant or a lose oil drain bolt. Yes – Synthetics (true ones at least) could have very well prevented that breakdown.

Also severe wear due to fuel and acids in the crankcase which AMSOIL addresses but a conventional Group II base stock cannot. At least when considering their price point which limits the quality of the additives.

Synthetics as you see in this report excel in viscosity retention and oxidation resistance. Federal Mogul published a study years ago showing the majority of engine failures (I think the figure was greater than 85%) were not because of contaminants but because of a lack of lubrication, excess heat or corrosion. AMSOIL products address all these and their sub-categories. Even if the subject changed the bargain brand every 50 miles, it won’t address viscosity loss when there is a overheating event causing deposits or metal fatigue.

Again the above are all features and insurance of Synthetics but the real draw is performance and is why I was sold on AMSOIL and later became a dealer thanks to it’s performance in 1960’s cars which I was told “It ain’t gonna work in them old cars!!” Lol!

Tag: additives

Why Motor Oil Deteriorates

Why Motor Oil Deteriorates

How oil becomes contaminated

Additive are designed to deplete

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