Previously on Propel Oil 101, we discussed just some of the fundamental components of oils and why they’re so important for your engine, we also went into the basic functions of a lubricant. If this doesn’t sound familiar, go back to our blog and take some time to review it! For those of you with the oil essentials, welcome back! We are going to get a bit more science-y and really look into the chemistry of what makes oil…oil.
So, as we talked about before, there’s a lot of things going on in your motor oil that helps to protect your engine from wear. But did you know there’s more to your oil than what meets the eye? Let’s break down some of the chemical compositions of your engine oil.
Base Oils
To start us off let’s take a look at base oils. A base oil is used to manufacture products including greases, motor oil and metal processing fluids. Oils require a specific base with particular compositions and properties in order to fulfil the needs of the application it is being used for. One of the most important factors is the liquid’s viscosity; keep this term viscosity in the back of your mind as we are going to come back to it in a bit. If you want to take a deeper dive into understanding base oils, refer to our previous blog, Oil 101: What Makes A Base Oil.
Engine Oil Additives
So that’s the majority of your engine oil, but, what’s in the rest of it? Well, additives of course! Supplemental chemicals, otherwise known as additives, are mixed into the base oil in order to meet the quality requirements for the end oil product. Additives enhance the base oil’s good properties such as viscosity, and improve the areas where it is deficient, like in rust inhibitors. While most of the end oil product is made up of the base oil, up to 10-20% of it can be additives, all to ensure your oil is up for the challenges thrown at it by today’s modern combustion engines.
Different Types of Additives
Dispersants and Detergents
Let’s take a closer look at some common oil additives. Dispersants and Detergents work as a team to help keep your engine clean. Dispersants are high molecular weight components with long hydrocarbon chains and polar sites that function to disperse sludge, varnish, and soot in the oil. Therefore, keeping these contaminants from forming harmful deposits on metal surfaces in your engine. Detergents are (C12-C24) alkenes containing soap molecules that have been over-saturated with CO2 to neutralize the acids formed from combustion, prevent metal corrosion, and reduce high-temperature deposits on pistons. They work in tandem with dispersants to ensure that any contaminants in your engine are swept away when you do your next oil change and that your engine stays clean throughout its regular use.
Antioxidants or Oxidation Inhibitors
Antioxidants or Oxidation Inhibitors prevent thickening when hydrocarbons are heated in the presence of oxygen. Oxidation is the general attack of the weakest components of the base oil by oxygen in the air. It occurs at all temperatures, all of the time, but is accelerated at higher temperatures and by the presence of water, wear metals, and other contaminants. It ultimately causes acids to form, which results in corrosion, and sludge formation. Oxidation inhibitors are also used to extend the operating life of the oil. They are a sacrificial additive that is consumed while performing their duty, therefore protecting the base oil. And they can be found in almost every lubricating oil and grease!
Corrosion/ Rust Inhibitors
Similarly, there are Corrosion/ Rust Inhibitors. Very few systems can completely exclude water. And since water is a necessary ingredient for the oxidative corrosion of metals, rust happens! Rust degrades metals itself, and generates particulate abrasives that can wind up causing wear. Through the use of corrosion inhibitors, polar molecules selectively cling to metal surfaces to form a barrier that excludes water. These additives act like sunscreen blocking out UV rays from burning your skin, except in this situation the UV rays are water and your skin is metal in an engine.
Pour Point Depressants(PPDs)
Pour Point Depressants, or PPDs, prevent waxy crystals from forming in your oil. Why do these crystals form? Well, the pour point of an oil is approximately the lowest temperature where it will remain fluid. In cold temperatures, paraffinic mineral oils can form wax crystals. These solid crystals form an intertwined network, like a spider web or beaver dam, that prevents the remaining liquid oil from flowing. So PPDs reduce the size of the wax crystals in the oil and their interaction with each other, allowing the oil to continue to flow even at low temperatures.
Foam Inhibitors
Foam Inhibitors are another additive, but they do something pretty interesting. Foam can be detrimental to your engine, as it allows pockets of air to form where you want your lubricants to be, resulting in metal-on-metal contact and wear. For those who operate heavy equipment, foaming in your hydraulic oil can compromise the performance of your hydraulic system. Foam Inhibitors reduce the formation and longevity of foam. This generally works by reducing the surface tension between oil and air. If the surface tension is reduced enough, any bubbles that manage to be formed will pop very quickly, as they are unable to hold themselves together.
Demulsifiers
Next is Demulsifiers; demulsibility is the capability of an oil to separate from water. When water gets into the oil, excessive churning can produce emulsions, which are poor lubricants for the average engine. As previously mentioned, water can also promote rust, foaming, and oxidation. Demulsifiers prevent the formation of a stable oil-water mixture, or an emulsion, by changing the tension of the oil so that water will amalgamate, and separate more readily from the oil. This is an important characteristic for lubricants exposed to steam or water so that free water can settle out and be easily drained off at a reservoir without total oil loss.
Emulsifiers
Emulsifiers are the exact opposite of a demulsifier and are used in oil and water-based metal-working fluids and fire-resistant fluids to help create a stable oil and water emulsion. The emulsifier additive can be thought of as a glue binding the oil and water together because normally they would like to separate from each other due to differences in tension and specific gravity. These emulsifiers are important for this kind of metal-working as they lubricate the cutting process while at low cutting speeds, cool the workpiece while at high cutting speeds, and flush any chips away from the cutting zone.
Viscosity Index improvers or Viscosity Modifiers
After that, we have a very important additive called Viscosity Index improvers or Viscosity Modifiers. These additives consist of a relatively small amount of polymer in a diluent base oil. As the oil heats up rather than letting the oil thin, the polymer expands resulting in the oil maintaining its viscosity. When the oil cools the polymer shrinks, and allows for the oil to remain flowing. It is through this expansion and contraction that the polymer allows the oil to retain a higher or lower contribution to the overall viscosity, depending of course, on the temperature of the oil. The goal is to have an oil that doesn’t get too thin at high temperatures, or too thick at low temperatures. Essentially, they function to reduce the influence of temperature on the viscosity of the lubricant.
Now we should talk about anti-wear and extreme pressure additives. Since they can easily be confused with one another as their jobs are pretty similar.
Anti-Wear and Extreme Pressure Additives
Anti-wear (AW) agents, usually use Zinc dialkyl dithiophosphate (ZDDP), to prevent excessive wear through metal-to-metal contact in the boundary or mixed lubrication regime. Boundary lubrication is when oil or grease creates a layer or border between two surfaces coming into contact, it’s like a no man’s land for lubrication. ZDDPs work by adhering to the metal surface and act as a sacrificial barrier to any potential wear that could happen. They also help protect the base oil from oxidation and the metal from damage by corrosive acids. Racecars or antique vehicles that have not been upgraded to modern standards require engine oil with extra ZDDP as they must endure intense wear and severe driving conditions.
Meanwhile, Extreme Pressure (EP) additives are more aggressive than AW additives. They react chemically with metal surfaces to form a surface film that prevents the welding and seizure of opposing asperities caused by metal-to-metal contact. They are activated at high loads and by high contact temperatures. Typically, you will see EP additives in gear oils, and you can blame them for giving most gear oils that unique, strong Sulphur smell. This is because these additives usually contain Sulphur and phosphorus compounds, and occasionally boron compounds. They can be corrosive toward yellow metals, especially at higher temperatures, and therefore should not be used in worm gears and similar applications where copper-based metals are used.
Overall, anti-wear agents (AW) tend to be used in the average, consumer-grade oil, while extreme pressure (EP) additives are used in more severe, and industrial applications.
There’s a lot that goes into oil, and each formulation from each brand name will have its very own special mixture. This is because most oil is customized to its particular application as seen with the differences between anti-wear and extreme pressure agents. This is why it’s so important to fill your vehicle’s oil based on the recommendations in your owner’s manual.
Viscosity
Now the term “viscosity” has been thrown around a lot here, but what does it mean and how is it related to motor oil? Well, viscosity is the measurement of a liquid’s resistance to flow; the higher the viscosity the “thicker” the fluid is and the less it moves around. A good Canadian example of viscosity is maple syrup. Maple syrup that’s been in the fridge will be slow to pour meaning it has a high viscosity. But maple syrup that’s been sitting on the table in the sunshine all day will readily pour out of the bottle, meaning it has a low viscosity. The higher the temperature the lower the viscosity and vice versa, this holds true for motor oil as well.
Viscosity is arguably the most important factor when selecting a proper oil or lubricant of any kind. This is because the viscosity aids in determining the level of lubricating film between moving parts. Too viscous of oil and your engine could be sluggish and less efficient, but not viscous enough and your engine could get damaged or seized. However, both high and low-viscosity oils are still useful. For example, low-viscosity oils are better suited for high speeds, low temperatures, and light loads. While high viscosity oils are used for slow speeds, high temperatures, and heavy loads. To find out the viscosity of your oil just look at the numbers on the bottle! Most oils you’ll see on any shelf will likely be mixed grade or mixed viscosity oils such as 5W30, but single grade motor oils exist as well even though they are not as common.
Aftermarket Additives
Okay so we covered additives in oil, but that begs the question… what about those aftermarket additives?
Well, when it comes to aftermarket additives there are plenty to choose from. But great consideration needs to be taken before tossing a bottle of some specialized additive into your oil, as they can sometimes cause greater harm than good. Here are two general rules to remember when thinking about using after-market additives:
- A low-quality lubricant cannot be converted into a premium product simply by the inclusion of an additive. In the world of lubricants, you get what you pay for. This is part of the reason why synthetic oils are so expensive, they have been refined to such a high standard that they are some of the highest-quality oils on the market.
- Base oils can only dissolve a certain number of additives. As a result, the add-on of supplemental additives into an oil that has a low level of solubility or is already saturated with other additives may simply mean that the new additive will settle out of the solution and remain in the bottom of the crankcase or sump. It may never carry out its intended purpose. Remember too much of a good thing can be just as detrimental as not enough.
If you choose to use any after-market additives or oil conditioners for a lubricated system, take the following precautions:
- Determine whether an actual lubrication problem exists. For instance, an oil contamination problem is most often related to poor maintenance or inadequate filtration and not necessarily poor lubrication or poor-quality oil.
- Choose the right supplemental additive or oil conditioner. This means taking the time to research the makeup and compatibility of the various products on the market, research truly helps.
The chemistry of oils can be as unique as the vehicle they’re getting used in and as the automotive industry continues to grow and evolve so does our need for proper high-quality engine oils. Nowadays there are higher operating speeds, temperatures, and environmental aspects and regulations to consider, all of which call for longer life and more highly refined petroleum oils.
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