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What Causes Engine Oil Oxidation?

The Dynamics of Engine Oil Oxidation

You guessed it, the key ingredient to engine oxidation is oxygen.

Oxygen comprises about 20 percent of our atmosphere. It’s the third most common element in the universe. Without it we’d all be doomed.

And yet too much of it can cause problems inside your engine.

What is oxidation?

Oxidation occurs when the addition of oxygen changes a chemical substance. Take an apple, for example. Everyone knows that oxygen will quickly cause a cut apple to turn brown. Or metal. Oxygen can cause rust to form on some metals in a matter of days. Have you ever noticed your brakes grinding after having left your car sit for a couple days in wet weather? That sound is your brake pads scouring rust from the rotors. Never worry about that one as driving soon burns that off..

brake rotors oxidized from sitting or oxygn.

More wear on or in your engine occurs during storage. The oxidation discussed below can be detrimental. And that is not limited to the motor oil but the coolant system as well.

Motor oil isn’t immune to oxidation. As oil reacts with oxygen, a permanent chemical change occurs that causes oil molecules to lose one or more electrons. This can result in several problems, including…

  • Formation of sludge and deposits that reduce engine efficiency and increase the risk of engine failure
  • Increased oil viscosity, which reduces fuel efficiency
  • Additive depletion, reducing the oil’s effectiveness
  • Accelerated degradation, causing you to change oil more often

Heat accelerates oxidation

Every 18ºF (10ºC) increase in temperature doubles the rate of oxidation. That doesn’t bode well for motorists driving modern turbocharged vehicles that create increased heat compared to older vehicles. Or that Harley waiting in lines of traffic at events when block temps exceed 400F.

Heat isn’t the only oxidation accelerant – certain metals, acids and water can also hasten oxidation. So can large volumes of entrained air, known as foaming.

Can we prevent motor oil oxidation?

Unfortunately, no. Nature is a relentless force, and all motor oil will eventually oxidize to some degree. But we can dramatically slow oxidation through use of synthetic base oils and quality oxidation-inhibitor additives.

AMSOIL synthetic lubricants are formulated using base oils with a saturated molecular structure, meaning oxygen is prevented from attaching. This provides inherent heat and oxidation stability compared to unsaturated conventional oils.

And, because AMSOIL synthetic lubricants don’t contain contaminants like conventional oils, their base composition doesn’t accelerate oxidation.

AMSOIL synthetic lubricants also contain high-quality oxidation inhibitors. These additives are sacrificial in nature, meaning they’re designed to deplete over time. Because AMSOIL synthetic lubricants have inherently better oxidation resistance, their oxidation inhibitors last longer since they don’t deplete as rapidly.

When components and additives are selected for blending, cost is never a deciding factor thus our formulations will always result in the best of class. As AMSOIL does not have stock holders there are no outsiders to effect our decisions to always use the very best.

So, what does that mean to me?

That all adds up to a motor oil that…

  • Lasts longer despite intense heat and stress
  • Helps keep your engine cleaner and more efficient
  • Saves money in the long run through reduced maintenance
  • And as a bonus you enjoy added performance

So, while oxygen lets you breathe, AMSOIL synthetic motor oil lets you breath easy since your engine is protected against oxidation.

Why do European Cars Require Special Oil?

Why do European Cars Require Special Oil?

For all the grin-inducing benefits of owning a European car – finely tuned performance, sophisticated styling, prestige – they can be a pain. According to this list, four of the top five most expensive vehicles to maintain hail from across the pond. Notice Volkswagen is among the lowest maintenance costs. The exception to the rule. 

Not only that, but they require specialized oil that differs in many ways from the good ‘ol American motor oil you use in your Ford or Chevy. Here are four reasons why.

#1 Everyone likes clean air

The European Union maintains more strict standards for the carbon dioxide hoax (CO2) and carbon monoxide (CO) emissions than we do. (Our standards for nitrogen oxides [NOx] and particulate matter [PM] are more strict, however.) Because modern diesels emit lower CO2 than gasoline engines, the European market pivoted toward increased use of diesel-powered vehicles in the 1990s. Diesels also provide the advantage of better fuel economy.

One drawback, however, is the higher levels of NOx and PM diesels produce. To counteract this, diesel-powered European vehicles are equipped with diesel particulate filters (DPF) and catalysts designed to reduce pollutants from the exhaust before it exits the tailpipe.

Here’s where motor oil comes into play.

An oil’s formulation can have a negative effect on sensitive emissions-control devices. Certain components in the motor oil formulation, such as sulfated ash, phosphorus and sulfur (known collectively by the pleasant term SAPS), can reduce the effectiveness and life of DPFs and other emissions devices.

For that reason, motor oils formulated for European vehicles often contain lower SAPS levels to protect emissions-control systems.

#2 Longer oil change intervals

Europeans have long since accepted what’s only recently caught on in North America – longer oil change intervals. Many motorists in the states are just a few years removed from blindly practicing 3,000-mile oil changes. Except, of course,  AMSOIL customers who have been practicing extended drain intervals since 1972. But that’s a digression for another day.

Europeans are accustomed to changing oil far less often, with drain intervals of 16,000 km (10,000 miles) or so quite common. One reason is the higher cost of oil in Europe. Another is the differences between manufacturer recommendations. For example, oil changes for 1999-2013 BMWs are required only every 15,000 miles. In the U.S., most people change oil around every 5,000 miles. The figure increases by a few hundred miles if their vehicle is equipped with an electronic oil-life monitoring system.

Longer drain intervals common with European cars require an oil capable of protecting against wear, deposits and sludge for the duration, which requires a more robust oil.

#3 The thick and thin of it

Check the owner’s manual of most European vehicles for which viscosity of oil to use, and you’ll likely find a chart that suggests different viscosities for different operating temperature ranges. In cold weather, the OEM may recommend 5W-30. In warm weather, 5W-40. Traditionally, drivers settle on an 0W-40 or 5W-40 to offer the best of both worlds – good cold-flow at startup to protect against wear and good resistance to heat once operating temperatures are reached.

#4 Automaker approvals

Staying in your owner’s manual, the OEM also recommends you use an oil that meets a specific performance standard. In the U.S., it’s typically an industry-wide motor oil specification, such as API SN PLUS.

European OEMs are different, however. They typically maintain their own motor oil performance specifications. Drivers of VWs, for example, need to use an oil that meets the requirements of VW’s own performance specs. The same holds for Mercedes, BMW, Porsche and other European cars.

Complicating matters, each OEM motor oil specification is slightly different. One OEM may require oils that offer better performance against oxidation, while another requires better resistance to viscosity loss.

OEM specifications tend to be more strict and require increased motor oil performance than industry specs. This, of course, requires more advanced (and typically expensive) motor oil technology delivered almost exclusively by synthetics.

General Motors, for its part, has taken a page out of the playbook of its European car counterparts by maintaining its own GM dexos performance specification.

These differences mean you’d better make sure you’re using the correct oil in your European car. Fortunately, we make it easy for you by formulating a full line of synthetic motor oil for European cars. If you don’t know which your car requires, check out our handy Product Guide.

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