What Happens to oil Making Me Needing to Change It?

Dan McClelland|Jan 07, 2020 8:36 AM

Regardless of its quality, every motor oil eventually loses its potency and must be changed to ensure peak engine protection. Let’s take a look at what happens to motor oil over time and why you periodically need to change oil.

Losing the base

Base oils are the backbone of the finished lubricant that ends up in your engine. Over time, they lose effectiveness due to the following 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 (113ºC), and even higher if towing or hauling.

The rate of oxidation for oil doubles for every 18°F (10°C) increase in temperature.

Moisture

Your vehicle is 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…yet another reason why you must change oil.

Viscosity is a motor oil’s most important property. The lower the viscosity, the faster the oils flows, like water. Thicker oils flow more slowly, like honey.

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. When this happens, it’s time to change your oil.

Shop AMSOIL Synthetic Motor Oil

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 you to change oil more frequently.

Additives: 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. Formulators add anti-wear additives 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.

While AMSOIL synthetic motor oil gives you the convenience of fitting oil changes into your schedule, it remains vital to install fresh oil at the appropriate time.

Shop AMSOIL XL 12,000 mile Synthetic Motor Oil

Engine Sludge Is Easily Avoidable

John Baker & Associates |Jul 24, 2019 4:20 PM

Engine sludge.

It’s a back gelatinous substance that wreaks havoc in engines. And long before the engine’s demise, engine sludge can foul engine sensors and interfere with performance. Some mechanics call it the “black death.”

How does motor oil, which is fluid, become a semi-solid paste or gel inside an engine?

Here’s what we’ll cover:

How engine sludge forms
The effects of engine sludge
Synthetic oil helps prevent engine sludge
High-quality additives fight engine sludge
Severe service invites engine sludge

How engine sludge forms

Engine sludge is the result of a series of chemical reactions.

The lubricant degrades as it is exposed to oxygen and elevated temperatures. The higher the temperature, the more rapid the rate of degradation. In fact, every 18°F (10°C) increase in temperature doubles the rate of oxidation.
Many people still believe any oil is fine as long as you change it often but 95% of the brands out there do not address that inch of protection when you really need it!! We’ve all had issues where the engine is overheating or some situation where adequate lubrication isn’t available. AMSOIL offers 75% more protection when you need it and our diesel oils offer 6X more protection than required by industry testing.

The by-products of this reaction form highly reactive compounds that further degrade the lubricant. Their by-products react with other contaminants, forming organic acids and high-molecular-weight polymeric products. These products further react, forming the insoluble product known more commonly as sludge.

What begins as a thin film of lacquer or varnish deposits on hot or cold metal surfaces and bakes into an expensive mess.

The effects of engine sludge

Sludge can block the oil passages and oil-pump pick-up screen, resulting in oil starvation. Often, the negative effects are cumulative rather than sudden.

Many engines with variable valve timing (VVT) use oil-pressure-operated mechanical devices to change valve timing, duration and lift. Sludge can plug the solenoid screen or oil gallies and impact the operation of VVT mechanisms, eventually leading to a costly repair bill. Sludge reduces efficiency and increases time and money spent on maintenance.

Who doesn’t want a cooler engine? Sludge, even the early stages prevents the engine from dispersing heat efficiently. Why would you risk a Group III “synthetic” which does leave deposits adding to or resulting into an engine which struggles to exhaust heat.

Synthetic oil helps prevent engine sludge

Fortunately, sludge and varnish deposits are something oil manufacturers can control. Using thermally stable synthetic base oils reduces the rate of degradation (oxidation). (Yes – and that is “Real 100%” Synthetics – not the ones they currently call “Fully”..

Anti-oxidant additives help reduce the rate of degradation as well. One of the most widely used is zinc dithiophosphate. Not only is it an excellent oxidation inhibitor, it is an outstanding anti-wear additive as well.

High-quality additives fight engine sludge

We can further address many of the issues occurring after the initial oxidation stage.

Additives, such as detergents and dispersants, are commonly part of motor oil formulation. They help promote the suspension of contaminants within the oil and keep them from agglomerating.

Detergents, which are also alkaline in nature, assist in neutralizing acids generated in the sludge-building process. Anti-oxidant, dispersant and detergent additives are consumed during use.

To achieve maximum life expectancy, use an oil with high concentrations of anti-oxidant, dispersant and detergent additives.

AMSOIL Signature Series Synthetic Motor Oil, for example, has 50 percent more detergents* to help keep oil passages clean and promote oil circulation. It provides 90 percent better protection against sludge**.

Signature Series Synthetic Motor Oil was subjected to the Sequence VG test to measure its ability to prevent sludge. Signature Series produced an oil pick-up tube screen virtually free from sludge. Our unique combination of detergents and high-quality base oils control oxidation and sludge to keep engines clean and efficient.

PDF of the test where AMSOIL has this done (Southwest Research)

Buy Signature Series

Severe service invites engine sludge

Equipment operating conditions also influence the likelihood of sludge or varnish issues.

Stop-and-go driving, frequent/long-term idling and operation in excessively hot or cold weather can increase the likelihood of sludge and varnish, especially if using more volatile conventional oils. If sludge has already formed, you can use an engine flush to clean sludge from your engine.

Interestingly, most auto manufacturers note in their owner’s manual that operation under any of the above conditions is considered severe service and requires more frequent oil changes.

From a mechanical standpoint, things like adding too much oil to the oil sump, antifreeze contamination, excessive soot loading, excessive oil foaming, poor engine-combustion efficiency, excessive blow-by and emission-control-system issues can all lead to the formation of sludge and varnish.

By practicing good maintenance and using properly formulated, premium synthetic lubricants, like AMSOIL synthetic motor oil, your vehicle won’t succumb to the “black death.”

Taking it a step further which many of our customers do – to make sure your vehicle is always running in peak condition one thing is to have your oil analyzed. I do it not so much to see how the oil is doing but to measure what may be going on in the engine to deplete detergents or to test for any out of typical wear levels, fuel in the crankcase, and to see if the viscosity is still on par. Oil analysis kits are easy to use especially when you have the dipstick extraction pump.

*vs. AMSOIL OE Motor Oil
**Based on independent testing of AMSOIL Signature Series 5W-30 in the ASTM D6593 engine test for oil screen plugging as required by the API SN PLUS specification.

Tag: sludge

Why Do I Need To Change My Oil?