Tagged: lubrication

Understanding the Different Engine Oil Change Intervals

At the beginning of this article, we reiterated that there are more than 5000 models of engines that exist. Every engine was built to different specifications, but they all provide the user with the ability to move the vehicle. With different manufacturers, there will also be varying oil specifications for each model, including the recommended oil change intervals. Let’s look at some of those.

Factors Affecting Oil Change Frequency

Lubricants are designed for certain conditions; however, if those conditions are exceeded, then the lubricant can degrade at a faster rate. For instance, if the driver frequently starts and stops or experiences prolonged periods of idling, these patterns can stress the oil more quickly, causing it to degrade.

Understanding the Different Engine Oil Change Intervals

If the fuel quality is not as expected, it may also contribute to the oil degrading more quickly. In such cases, users may opt for shorter oil change intervals to ensure their engine remains protected.

Another factor affecting the frequency of oil changes is the quality of the oil used. Typically, synthetic oils may have longer oil change intervals than mineral oils. However, there are some cases where the manufacturers advise the same interval length, whether mineral or synthetic.

Using Oil Analysis to Determine Engine Oil Life

There are instances where the oil drain interval can be extended beyond the manufacturer’s recommended interval. However, this must be done with guidance from a lab while utilizing oil analysis. Typically, some applications do not utilize the additives in the oil as quickly and may not require the regular oil change interval; instead, the oil remains healthy by the time it’s supposed to be discarded.

This can be considered a waste of resources. With oil analysis, one can monitor the health of the oil and determine if it is nearing the end of its useful life, allowing for informed decisions on whether to change it or not.

The Debate over Extended Oil Change Intervals

There will always be a debate over whether it is wise to extend the oil change intervals for equipment, as it goes against the manufacturer’s recommendations (or, in some cases, this could void the warranty). However, just as with blood testing (or condition monitoring for oil), close monitoring allows us to justify the outcomes of extending the intervals.

Some of the benefits of extending the intervals include reduced manpower, allowing staff to perform other critical duties, a reduction in oil consumption and its disposal, as well as reduced downtime for maintenance. One can also include the reduction of safety risk depending on the application. These all add up in the end, and the benefits of safely extending the intervals may outweigh remaining at the recommended intervals.

Find out more in the full article featured in Precision Lubrication Magazine.

Automotive / Oil Properties / Strategic Tips

Benefits of Using the Right Engine Oil

As we’ve covered in this article, various types of engines require different levels of performance, and engine oils have been specifically designed for these conditions. Hence, it becomes critical to select the right engine oil for your engine. But what are some of the benefits of selecting the right oil?

Improved Fuel Efficiency

Firstly, the primary purpose of a lubricant is to reduce friction between contacting surfaces. By reducing the friction, a smaller amount of energy is required to perform the same amount of work. Overall, this leads to a more efficient system.

When we’re talking about engines, fuel is also required to produce energy for the engine to work. As engine oils have become more advanced, they have enabled significant improvements in fuel efficiency for many engines. This is one of the requirements in the API service categories. By selecting the incorrect viscosity of oil or type of oil for your vehicle, you can negatively impact the fuel efficiency, which in turn adds up to a higher fuel bill at the end of the month!

Longer Engine Life

The occurrence of wear is one of the most common challenges with engines. By using the correct oil (as recommended by the manufacturer), the viscosity of the oil is ideal for keeping the engine surfaces from touching, which can prevent wear.

Additionally, engine oils contain additives that can also help protect the oil and the engine’s components. Hence, with the right oil (as specified by your OEM), your engine will have the ideal conditions it needs to last longer compared to using an oil that does not provide the optimal protection.

Better Engine Performance

Engines were created with particular standards in mind. OEMs designed engines to withstand certain temperatures and conditions. These attributes are passed to lubricant suppliers who would design engine oils capable of withstanding and performing in these conditions. Using the recommended engine oil ensures better engine performance.

For instance, if the customer decides to use an API CK4 oil in their diesel engine but uses 500 ppm sulphur fuel, they can run the risk of poisoning their catalyst or damaging their aftertreatment devices. This would not lead to better engine performance! Therefore, it is essential to follow the OEM’s recommendations to achieve optimal engine performance.

Reduced Emissions

Many of the newer specified oils are designed to reduce emissions. However, the older spec oils were not developed with reducing emissions in mind. Hence, using an older-specification oil (API SL) in a vehicle manufactured in 2024 may not necessarily help reduce emissions. On the other hand, the API SP oil is designed with enhanced emission control in mind, making it ideal for reducing emissions.

Enhanced Lubrication and Protection

If we recall the straw example from earlier in this article, we will realize that engines have been designed for specific lubricants, both in terms of viscosity and additive packages. By using the recommended lubricants, we can ensure that our engines receive the necessary protection and have the correct amount of lubrication to prevent wear. Use lubricants specifically designed for your engine to ensure enhanced lubrication and protection.

Find out more in the full article featured in Precision Lubrication Magazine.

Automotive / Oil Properties / Strategic Tips

Types of Engine Oils

When you walk into the auto repair store, it can be quite overwhelming with the barrage of oils readily available for customers. It’s easy to get distracted by the shiny packaging or marketing claims (‘This is the best oil ever!’) when deciding to purchase oil for your vehicle. However, it begins with understanding the basics of engine oils.

Conventional Oil

This is the oil that has been around since the beginning of the automotive revolution. They are also referred to as mineral oils and represent the API Groups I-III base oils. Ideally, these oils can be traditionally found as the base for lubricants that are on the higher end of the viscosity spectrum (think 40, 50, and 60 weight).

These mineral oils are found on the earth, and their molecules may not all be the same size (unlike synthetic oils). They are usually less costly than synthetic oils but still provide some protection to the engines.

Synthetic Oil

Synthetics are considered the top-tier set of lubricants, as they can withstand harsher conditions compared to mineral oils. They are found in groups IV and V, and many of them are man-made, while others are naturally occurring. Most of their molecules are the same size, allowing for better properties, and they tend to be more expensive than mineral / conventional oils.

Synthetic Blend Oil

A synthetic blend oil refers to an oil that contains both synthetic and mineral base oils. However, there is no set ratio of synthetic to mineral oil that can impact the final performance of the lubricant to be classified as a synthetic blend. Many manufacturers can easily get away with using only 1% synthetic oil blended with 99% mineral oil and still label the oil as a “Synthetic blend.”

This gives the customer the false impression that they are purchasing an oil that will offer the best of both worlds.

High Mileage Oil

Until about a decade ago, high-mileage oils were not really that popular, but with the aging population of automobiles, there has been a significant increase in the purchase of this type of oil. Different manufacturers have varying specifications for these oils and typically use the vehicle’s mileage range to help guide customers in selecting the correct oil.

These oils are blended on the “thicker” side of the viscosity range, meaning on the higher end of the maximum viscosity. For instance, a regular 10w40 would appear to be “thinner” than a High Mileage 10w40. They are also reinforced with seal conditioners to help some of the seals in the older engines. But it does not contain magic, so it can’t repair your engine!

Racing Oil

The performance required of a Ferrari compared to that required of a minivan can differ drastically. The operating conditions are starkly different, and the engines would require specifications from their manufacturers. As such, there are specially developed racing oils for these higher-performance vehicles built to withstand harsher conditions compared to the regular engines.

This does not mean that you should use racing oil in your regular vehicle to get the performance of a race car. The oils are blended for specific purposes and must be used accordingly to ensure maximum functionality. Similarly, the oil used in the minivan would not be able to withstand the conditions of a racing car. Use oil that is compatible with the type of engine and the required performance.

Find out more in the full article featured in Precision Lubrication Magazine.

Automotive / Oil Properties / Strategic Tips

Common Misconceptions about Viscosity and Engine Oil Grades

Many people believe that “thicker” oil is better for their vehicle. This is the furthest thing from the truth! Over the years, engine sizes have been reduced dramatically. With this size reduction, we can infer that the clearances within the engines have also decreased. Hence, a “thicker” oil from 50 years ago will not suffice in a modern-day engine.

Think of trying to drink molasses with a thick (or wide) straw. This may be possible (although challenging), but if we swapped the thick straw for a thinner, narrower straw, the person would have to use significantly more force to pull up the molasses. A similar phenomenon occurs with engine oils.

Common Misconceptions about Viscosity and Engine Oil Grades

In modern engines, the oil lines are narrower, so trying to force a heavier-weighted oil (such as straight 50) would put more pressure on the engine. This is where we begin to see leaks in the engine, particularly at the bottom of the sump near the seals, where the most pressure is exerted during start-up to pump the thicker oil to the top of the engine. However, if we used the correct viscosity of the oil, the engine would not be subjected to this amount of additional pressure. So “thicker” is not always better.

Another common misconception is that the number in front of the “w” in a multigrade oil represents the thickness of the oil, and if it’s zero, then it must be very thin! The number in front of the “w” for multigrade oils represents the viscosity of the oil at start-up conditions (typically 0°F or -17.8°C for Winter).

Hence, the lower the number, the faster the oil will flow at startup. As such, a 0w20 will get from the bottom of the sump to the top of the engine faster than a 20w50. In this case, the 0w20 will provide more protection during startup compared to the 20w50, as most wear occurs during this period.

On the other hand, the number behind the “w” indicates the viscosity at operating temperature. This is where a higher number may not always be agreeable, depending on the year of manufacture of your engine or the ambient conditions. When deciding which oil to use, both numbers (in front of the ‘w’ and behind the ‘w’) are important.

Find out more in the full article featured in Precision Lubrication Magazine.

Automotive / Oil Properties / Strategic Tips

API & ILSAC Certification

API Certification

The American Petroleum Institute has a dedicated Engine Oil Licensing and Certification System (EOLCS), a voluntary license and certification program that authorizes engine oil marketers who meet the specified requirements to use their quality marks.

It is a cooperative effort amongst additive industries and vehicle and engine manufacturers such as Ford, General Motors, and Fiat Chrysler, which are represented by the Japan Automobile Manufacturers Association and the Truck and Engine Manufacturers Association. The performance requirements and test methods are established by vehicle and engine manufacturers, as well as technical societies and trade associations, including the ASTM, SAE, and the American Chemistry Council (ACC).

Figure 2: API’s Shield vs Starburst

While the API initially included designations for both gasoline and diesel specifications, it later established these as two separate classes. Gasoline engines designed for cars, vans, and light trucks were allocated to the “S” or Service category. On the other hand, diesel engines designed for heavy-duty trucks and vehicles fall under the “C” or Commercial category.

These standards have been in place since 1947 and regulate both gasoline and diesel engine oils. One of the major changes since 2020 is the introduction of 0w16 oils, which now have their certification mark, the “shield” instead of the traditional “starburst”.

What’s the main difference between ILSAC GF-6A & 6B?

Both are designed to provide protection against low-speed pre-ignition (LSPI), timing chain wear protection, improved high-temperature deposit protection for pistons and turbochargers, more stringent control of sludge and varnish, enhanced fuel economy, and protection of the emission control system for engines operating on ethanol-containing fuels up to E85. However, ILSAC GF-6B applies only to 0W-16 oils.

The current gasoline engine oil standard is API SP. This standard was introduced in May 2020 and is designed to protect against low-speed pre-ignition (LSPI), provide timing chain wear protection, enhance high-temperature deposit protection for pistons and turbochargers, and implement more stringent control of sludge and varnish.

API SP with Resource Conserving matches ILSAC GF-6A by combining API SP performance with improved fuel economy and enhanced emission control system protection for engines operating on ethanol-containing fuels up to E85.

Figure 3: API SP Service Donut

On the diesel side of things, there has been a slight break from tradition, as two new categories, CK-4 and FA-4, have been introduced. The main difference with these is the type of fuel used, specifically in terms of its sulphur concentration. CK-4 is ideally used for vehicles using diesel fuel with 500 ppm (0.05% weight) sulphur, while FA-4 is used for vehicles using diesel fuel with less than 15 ppm (0.0015% weight) sulphur, and they must be Xw30 oils.

Figure 4: API CK-4 Service Donut

CK-4 oils are used in high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway and Tier 4 non-road exhaust emission standards, as well as previous models of diesel engines. They are formulated for use with diesel oils containing up to 500 ppm sulphur. However, if they are used alongside fuels containing more than 15 ppm sulphur, this can affect the exhaust after-treatment system durability or oil service drain interval.

They effectively sustain the durability of emission control systems, particularly when particulate filters and other advanced after-treatment systems are employed.

API CK-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration, as well as protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low- and high-temperature properties, and soot-related viscosity increase.

FA-4 oils are specifically for certain Xw30 oils formulated for use in high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway greenhouse gas emission standards. They are formulated for use in on-highway applications with diesel fuel sulphur content up to 15 ppm. These oils are blended to a high-temperature, high-shear (HTHS) viscosity range of 2.9cP – 3.2cP to assist in reducing greenhouse gas (GHG) emissions.

They are effective in sustaining the durability of emission control systems, particularly when particulate filters and other advanced after-treatment systems are employed.

API FA-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration in addition to protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low and high-temperature properties, and soot-related viscosity increase. It is essential to note that FA-4 oils are not interchangeable or backward compatible with API CK-4, CJ-4, CI-4, CI-4 PLUS, and CH-4 oils.

An exhaustive list can be found here.

Figure 5: API FA-4 Service Donut

Find out more in the full article featured in Precision Lubrication Magazine.

Oil Properties

Frequently Asked Questions About Machinery Lubrication

How Often Should Equipment Be Lubricated?

This can change depending on your environment and operating conditions. A machine operating in a clean environment with ambient temperatures and a typical load should be lubricated according to its schedule. However, if this same machine is in a dusty, high-temperature environment working 24/7, its change or relubrication intervals will be shorter than the regular ones.

Lubrication reduces friction in your system. Hence, you can detect when friction levels increase if you’re monitoring your assets using ultrasound. This would allow you to apply a small volume of lubricant to lower these levels. (This is specifically for greases.)

You are always advised to check with your OEM, who will have recommended lubrication schedules for your equipment in varying environments and operating conditions.

Frequently Asked Questions About Machinery Lubrication

What Are the Signs of Poor Lubrication?

Poor lubrication can mean under- or over-lubricated assets or incorrect use of a lubricant in a particular application. If your lubricant is not meeting the expected intervals and the components constantly fail due to lubrication issues, these are some telltale signs of poor lubrication.

How Do I Know If I’m Using the Right Lubricant?

All lubricants are required to meet standards to prove their performance, or OEMs may approve some for their suited applications. The lubricant’s performance standards should be compared to those outlined by the OEM for a particular piece of equipment. If they don’t match or there are discrepancies, then the OEM or lubricant supplier should be contacted for verification. Sometimes, an over-qualified lubricant may be used in your application, and it can also give you the expected results, but of course, at a higher cost.

Lubricants are the lifeblood of our equipment and keep our industry moving. We need to understand them fully, their roles in our equipment, and how we can optimize them for maximum performance.

References

Debshaw, B. (2023, February 02). Reducing Costs, Increasing Production: The Remarkable Impact of Predictive Maintenance. Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/predictive-maintenance/
Mathura, S. (2024, April 01). Lubricant Additives: A Comprehensive Guide. Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/lubricant-additives/
Mathura, S. (2023, March 26). Oil viscosity: A practical guide. Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/oil-viscosity/
Britton, R. (2023, January 26). How do Solid Lubricants work? Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/solid-lubricants/
Hamrock, B. J., Schmid, S. R., & Jacobson, B. O. (2004). Fundamentals of Fluid Film Lubrication Second Edition. New York: Marcel Dekker Inc.
Pirro, D. M., Webster, M., & Daschner, E. (2016). Lubrication Fundamentals, Third Edition, Revised and Expanded. Boca Raton: CRC Press.
Pirro, D. M., Webster, M., & Daschner, E. (2016). Lubrication Fundamentals, Third Edition, Revised and Expanded. Boca Raton: CRC Press.
Hamrock, B. J., Schmid, S. R., & Jacobson, B. O. (2004). Fundamentals of Fluid Film Lubrication Second Edition. New York: Marcel Dekker Inc.

Find out more in the full article featured in Precision Lubrication Magazine.

Oil Properties

Lubrication Maintenance Best Practices

We’ve already covered some mistakes; it’s time to look forward to some lubrication best practices. To some of us, these may seem trivial, but they can lead to big impacts on your overall maintenance budget and can even manage to decrease some unplanned downtime.

Creating a Lubrication Maintenance Schedule

Every component in your industrial facility needs to be lubricated. The frequency at which this occurs, alongside the type of lubricant, can vary greatly. However, by properly mapping out your lubrication points and frequency intervals, you can develop a lubrication maintenance schedule that your planner will be proud of!

The first task on your list would be to have a detailed listing of all your assets, their locations, the type of lubricant being used, and suggested relubrication frequency. Next, this can be consolidated into daily, weekly, monthly, and quarterly tasks.

Afterward, you must bring your mapping skills into place as you incorporate the lubrication tasks with other maintenance tasks in the same area. This way, your assigned personnel maximize their time in one geographical location.

Importance of Lubricant Analysis and Condition Monitoring

How often do you perform blood work for yourself or visit your doctor? Performing blood work is similar to taking an oil sample for our equipment as we investigate what’s happening inside it. This can give us a heads-up on an impending failure (if there is a high wear metal concentration or the presence of contaminants) or an issue in the oil (changes in viscosity or additive packages).

By effectively monitoring the health of your oil, you can prevent unplanned shutdowns or even extend its life. This can save your company from significant losses and increase your production output.

Lubrication Training for Maintenance Teams

Quite often in our industry, we hear, “Oil is oil, or grease is grease,” but after reading this article, I’m sure you will agree that those words are a very big misrepresentation. This is why training is so important for our teams. We want to ensure we all understand why we’re not leaving the oil drums out in the rain and pouring them into our equipment!

This will lead to water getting into the oil drums. Then, we include the water in our equipment alongside our oil, which will change the oil’s viscosity, possibly leech out some of the additives being used for protection, and can act as a catalyst for further, rapid degradation of the oil.

This simple storage and handling concept can cost our company unplanned downtime and loss to production, but by adequately training our teams to understand lubrication and some of the best practices, we can transform our facilities into world-class lubrication sites. The only way to do this is as a team working together to achieve a goal that we all understand.

Find out more in the full article featured in Precision Lubrication Magazine.

Oil Properties

Common Lubrication Mistakes and How to Avoid Them

Mistakes can happen all the time, but when we repeat them, they can become a habit or, worse, be viewed as a “best practice” within our industry. In the lubrication realm, there are a few common mistakes that occur quite frequently. In some cases, the operators may not understand or be aware of the full gravity of these mistakes. In this section, we will explore ways to avoid these mistakes.

Over-Lubrication vs. Under-Lubrication

“Some grease is better than no grease” is a common saying in the industry. However, there is such a thing as over-lubrication! Think about swimming pools. The pool usually has different levels: a minimum fill level, then a mid-tier level, and finally, the maximum level.

Common Lubrication Mistakes and How to Avoid Them

Over-lubrication of a bearing

If we don’t fill it to the minimum level, it’s basically a puddle of water, not a swimming pool. We need a certain volume of water to function as a swimming pool. The same applies to our equipment.

We will under-lubricate our equipment if we do not provide enough grease or oil. In these cases, there is not enough lubricant to form the full required film to keep the two moving surfaces apart and perform all the lubricant functions. Therefore, there will be increased friction, wear, and heat, all leading to system inefficiencies.

On the other hand, if we filled the swimming pool beyond the maximum level, it would be pretty tricky for us to stand in it (while touching the bottom) or walk across the length of the pool without having lots of opposition from the water compared to walking across the length of the pool when it’s filled mid-way.

Something similar is happening with our equipment. If we over-lubricate it, we place additional stress on the components to perform extra work, as they must move on a thicker layer of lubricant, which will cause frictional losses. This can cause the equipment to heat up, leading to degradation of the lubricant and loss of efficiency.

Both over-lubrication and under-lubrication can be detrimental to your equipment. Instead, use the optimal level of lubricant, or (in the case of greases) use ultrasound to determine the required amount of grease for your application. In both cases, the ideal amount of lubricant is the volume at which the coefficient of friction is significantly lowered.

Choosing the Wrong Lubricant for the Application

Quite often, the wrong lubricant is chosen for the application. This can happen in several ways, whether unintentional or an error passed down through shift changes. Selecting the correct lubricant for your application begins with knowing the environmental and operational conditions and the equipment specifications.

Your first guide/resource should be the equipment’s OEM. They designed the equipment to perform within specific tolerance limits and can advise on the most appropriate lubricant given these tolerances. If they cannot be contacted, an alternative would be contacting your lubricant supplier to help determine the best lubricant based on their expertise with similar types of equipment in varying conditions.

Selecting the correct lubricant for your application begins with knowing the environmental and operational conditions and the equipment specifications.

Another misconception about selecting lubricants is that they should be chosen based on their initial cost. Instead, the total lifecycle cost of the lubricant should be considered, and the properties of the lubricant should also be factored into the decision-making process. The initial cost of the lubricant pales compared to the cost associated with unplanned downtimes, the short life span of the lubricant, and its disposal.

Inadequate Lubricant Storage and Handling

Lubricants should be handled with care. They can be affected by temperature, light, water, particulate, or even atmospheric contamination. They must be stored properly in a dry, clean, cool space (not exposed to the elements).

When transferring lubricants from larger containers into smaller ones, think of how you would perform this operation if you transferred blood from the blood bank to one of your family members. Would you use any container you found on the ground, or would you ensure that it is a sterilized container (needle or equipment)?

Lubricants can easily become contaminated with particulates, which can then be transferred to machines, leading to unplanned shutdowns. When transferring lubricants, it is critical to ensure that we do not introduce contaminants or transfer these contaminants to our equipment. We must keep the lubricants clean and free from contaminants.

Ignoring Environmental and Operational Conditions

Not all lubricants are created equally. Some are designed for harsher environments, while others can only function in regular operating conditions. Mineral oils can typically work in many circumstances. However, when higher temperatures or loads are involved, this may be a job more suited for a synthetic lubricant.

On the other hand, if the lubricants are geographically close to waterways or come into contact with them in any way, then these should be environmentally acceptable lubricants (EALs). Depending on the load and temperatures experienced by your equipment, your lubricant provider or OEM for the machinery can advise on the best-suited lubricant that will perform in these conditions.

Find out more in the full article featured in Precision Lubrication Magazine.

Oil Properties

Lubrication Regimes: Understanding the Science of Lubrication

The primary purpose of lubrication is to create an acceptable lubricant film to sufficiently keep the two moving surfaces apart while allowing them to move with reduced friction. This is the ideal condition, but a lubricant can undergo a couple of different regimes before it achieves this full film format.

The figure below shows the overall relationship between film thickness and the related regime and the associated regime relationships with the coefficient of friction.

Lubrication Regimes Understanding the Science of Lubrication

Stribeck curve showing the friction levels associated with the various lubrication regimes from Lubricants and Lubrication, Second, Completely Revised and Extended Edition edited by Theo Mang and Wilfried Dresel (2007)

Boundary Lubrication

At startup or rest, lubricants are usually residing in the sump. For this example, let us think about a car at rest. Since the vehicle has not moved, all the oil should have been drained and settled in its sump at the bottom of the engine. When the car starts, all the parts on the inside will begin moving.

Only after it starts does the oil begin its swift journey from the bottom of the sump to all the moving parts. That means that there is a delay between the oil getting to perform its function or reaching the moving parts.

In boundary lubrication, the oil has not fully formed its film, and there isn’t adequate separation of the asperities.

During boundary lubrication, the oil has not fully formed its film, and there isn’t adequate separation of the asperities. In this state, wear can still occur, and it is in this state that most wear occurs. A similar situation occurs during equipment shutdown, where the components also experience this boundary state of lubrication.

The figure at the side shows the various film conditions. In boundary lubrication (c), the asperities touch, whereas they are fully separated in (a).

Surface-active additives are critical for boundary lubrication and become activated under certain conditions. One of the most popular additives is EP (Extreme pressure) additives, which become activated when temperatures are increased (usually as a result of increased friction).

A surface film is typically formed during boundary lubrication. This can be the result of physical adsorption (physisorption), Chemical adsorption, or Chemical reactions involving or not involving stearate.

Different regimes as it relates to the lubricant

Physical adsorption occurs under mild sliding conditions with light loads and low temperatures. Chemical adsorption (chemisorption), stronger than physisorption, occurs when fatty acids react with metals to form soaps, which may or may not be attached to the surface.

On the other hand, chemical reactions that do not involve a substrate allow for slightly stronger bonds than chemisorption. However, with phosphorus-containing compounds, the phosphorus exists in a soluble carrier molecule that degrades at elevated temperatures, plates out on the metal surfaces, and forms a phosphorus soap (typically found in the Antiwear additive packages).

The last and strongest bonds to protect the surface are the chemical reactions involving a substrate where sulfide layers are formed on the surface. These provide low friction and good adhesive wear resistance⁵.

Mixed Lubrication

This state of lubrication exists as the lubricant transitions between Boundary and Full-Film lubrication. Its average film thickness is less than 1 but greater than 0.01μm. Some exposed asperities and roller element bearings can still experience this state during their start-stop cycles or if they are experiencing excessive or shock loads. These thin films are exposed to high shear conditions, leading to increased temperatures and reducing the lubricants’ viscosity⁶.

During this state, antiwear and EP additives protect the surfaces (similar to boundary lubrication). Most lubricants transition through this phase, and the additive packages must be able to help protect the surfaces.

Hydrodynamic Lubrication

Coefficient of Friction for the various regimes

During this regime, the two surfaces are usually fully separated. They are thick hydrodynamic fluid films that tend to be more than 0.001 inches (25μm) in depth, experiencing pressures between 50-300psi⁷. Ideally, friction only results from the shearing forces of a viscous lubricant⁸.

In this state, the surfaces are conformal, meaning that the angles between the intersecting surfaces remain unchanged. It is important to remember this, as it differentiates the hydrodynamic regime from the elastohydrodynamic regime. As shown in the figure below, the coefficient of friction changes for the various regimes, with the hydrodynamic regime having the lowest value.

Elastohydrodynamic Lubrication (EHL)

One of the main defining factors with EHL is that the oil’s viscosity must increase as the pressure on the oil increases, such that a supporting film must be established at the very high-pressure contact areas. Due to the pressure of the lubricant, elastic deformation of the two surfaces in contact will occur. These films are thin, typically around 10-50 μinches (0.25 – 1.25μm).

The surfaces in EHL are non-conformal (unlike Hydrodynamic lubrication), and the asperities of the contacting surfaces do not touch. However, the high pressures can deform either of the contacting surfaces to ensure that a full fluid film is maintained. This can increase the coefficient of friction.

Find out more in the full article featured in Precision Lubrication Magazine.

Oil Properties

Types of Lubricants and Their Applications

Not all lubricants are created equally! In fact, they need to be designed differently for the various applications in which they are to be used. Typically, the overarching classification of lubricants can fall under either oil or grease. However, there are further categorizations that also include solid lubricants and specialty lubricants, as there are many varying applications of lubricants.

Oil Lubricants: Characteristics and Uses

Most of us are very familiar with oils. They are liquid; we use them in our cars or trucks, but what are they? An oil is comprised of base oil and additives. The additives can be used to either enhance, suppress, or add new characteristics to the base oils².

Types of Lubricants and Their Applications

Typically, oils can be used in many different applications and provide the advantages of having various viscosities according to the application3. These can range from oils with a viscosity similar to that of water to oils as thick as tar.

One of the main advantages of using oils as lubricants is their ability to dissipate heat from the system. Since they are fluid and circulate, they can “move” heat away from specific components and even help to remove some contaminants.

Oils can be used in gasoline-engine passenger cars, diesel-engine applications, circulating systems, turbines, gear applications, hydraulics, compressors, or even natural gas engines. Each application represents a different ratio of additives to base oils, ranging from 30% (motor oils) to a mere 1% additive (turbine oils).

Grease Lubricants: Advantages and Limitations

While the industry is familiar with oils as lubricants, there are some places where grease works better than oils! Greases are oils to which a thickener has been added. As such, they comprise base oil, additives, and thickener. The thickener holds the oil in place, allowing it to perform its main functions of reducing friction and providing lubrication.

One of the main advantages of greases is their ability to stay in one place. Consider a bearing placed at a 90° or 180° angle. If oil were used to lubricate this, it would drain out very easily. However, grease stays in place and still ensures that lubrication occurs.

While staying in place is a major advantage of grease, there are also some disadvantages to using it. A couple of those include the fact that grease cannot transfer heat away from components and keeps contaminants in place. These can both negatively impact the equipment.

Similar to oil, grease has different viscosities as per the NLGI (National Lubricating Grease Institute). These range from a 000 (almost the consistency of oil) to a 6 (similar to that of a block) and are all made for varying applications, as shown in the figure below.

While these viscosities define the application, one must also remember that the base oil viscosity can also differ. As such, operators must be mindful of NLGI grade, base oil viscosity, and additive package when selecting an appropriate grease.

Solid Lubricants: When and Why to Use Them

Why do we need a solid lubricant if we already have oils and greases in different states? Particular applications make these lubricants mandatory as they are the only ones that can meet the conditions and specifications involved.

Unlike oils or greases, these solid lubricants are designed to work in one lubrication regime, boundary lubrication⁴ (more on this later in the article). What sets these lubricants apart is their ability to form very thin films on the surfaces of moving components, which reduces friction due to their very low shear strength.

Some examples of solid lubricants include graphite, Molybdenum Disulfide (MoS2), Boren Nitride, and Fluoropolymer (PTFE). These solid lubricants can usually be used as grease additives (such as MoS2 for greases in mining with high load, low-speed applications) or even in the space industry for dry lubricant coatings on spacecraft.

Find out more in the full article featured in Precision Lubrication Magazine.