What are Fire Resistant Lubricants?

Fire-resistant lubricants are fluids that are used in applications and systems where the risk of ignition is high. Typically, these environments are near or contain: open flames, sparks, or hot metals. If an oil leak were to occur, the risk of injury, damage, and even death is magnified as sustained fires can occur. That is why fire-resistant lubricants have been developed and manufactured to protect personnel and equipment.

Why do I need a Fire-Resistant Lubricant?

Fire-resistant lubricants are most needed in environments need high-temperature surfaces and open flames. Regular fluids that have low flash points pose the greatest risks to fire and should be switched for fire-resistant lubricants that have higher flash points.

If using pressurized hydraulic lines, it is key to have a fluid with a high flash point as small leaks can aerosolize the lubricant easily. The lubricant spray is much more susceptible to fire. It takes much less heat to ignite and can spread to fluid reservoirs. The lubricant can ignite if it’s fire point and/or auto-ignition point is reached. The fire point is the temperature at which a fire is sustained and is typically several (50+) degrees higher than the flash point. Opting for fire-resistant fluids with higher flash points will reduce the risk of fire and damage.

Fire-Resistance Fluid Standards

The term “Fire Resistant” and “Fire Resistance” are often misinterpreted and sometimes overused. There is no single property or metric that conveys relative fire resistance. Metrics like flash point, fire point, and autoignition temperature are useful, but do not tell the whole story. Because of this, most fluids are vigorously tested and are classified as “fire resistant” if it can pass various tests and simulations.

The Factory Mutual Research Corporation (FM) developed key benchmarks for testing fire-resistance. FM tests every single commercially available “Fire Resistant” fluid to ensure it meets various benchmarks. FM 6930 is the standard for hydraulic fluids and is classified into 3 levels: 0, 1, and 2. This standard only measures a fluid’s flammability and does not consider other factors of the lubricant.

The Mine Safety & Health Administration (MSHA) has their own tests and standards for underground mines and applications. Their stringent testing produces more failures than FM. Both programs has strict auditing and inspection programs to ensure fire-resistant fluids meet performance standards.

Types of Fire-Resistant Lubricants

Oil-Water Emulsions

There are 2 types of oil-water emulsion fluids: oil-in-water and water-in-oil. Oil-in-water emulsions are formulated with oil droplets sustained in water. Approximately 95% of the fluid is made of water and the remaining 5% is composed of oil. These emulsions have excellent fire resistance and heat-transfer capabilities, but poor lubricity and poor corrosion protection.

Due to these poor lubricity characteristics, water-in-oil emulsions (also known as inverse emulsions) are better performing fluids. These are 40% water and 60% oil. It provides more balance of heat-transfer properties, lubricity, and corrosion protection. The fire-resistance primarily comes from the water, which turns into steam and reduces the oil’s combustibility.

Water Glycols

Water-in-oil emulsions have seen declining market share due to the rise of Water Glycol Fluids. Water Glycols contain 35-45% water and the remaining contents are some sort of glycol, such as ethylene glycol. These Water Glycols offer some benefits such as a lower freezing point and excellent fire resistance. Water Glycols do have drawbacks, but many of these can be mitigated by various additive packages. These fluids can be used in a variety of applications, but speed and strength ratings are reduced due to the limited performance of the fluid. Despite this, Water Glycols are one of the most popular fire resistance lubricants on the market today.

Phosphate Esters

Phosphate Esters provide the best fire resistance properties of any fluid. This is due to their natural molecular structure. They are non-corrosive, have excellent oxidative stability, great anti-wear characteristics, and are suitable for use up to 150 C. Despite this, they have been losing popularity due to stringent compatibility and maintenance concerns. They are still popular for aircraft and military applications. Additionally, they require special seals and coatings and require special care during disposal.

Polyol Esters

Polyol ester fluids have gained popularity due to its fire resistance properties, excellent lubricity, and good viscosity stability across different temperatures. These contain additive packages to impart good performance and high thermal properties. These are much more compatible and versatile than phosphate esters. This has led to their rising popularity and market share in recent years.

Maintenance and Other Considerations

When switching to fire-resistant fluids, compatibility must be considered before restarting the equipment. By carefully draining the machine, this decreases the likelihood of any incompatibility issues.

High-water content fluids require a lot more maintenance and care to ensure they perform properly. Water provides a great medium for bacteria and biocide treatments are recommended to prevent bacteria growth. As temperatures rise, water evaporates and needs to be replaced to ensure the fluids cooling properties are not compromised. pH levels should be monitored along with corrosiveness and wear protection. It is important to follow proper storage practices to maximize efficacy and shelf life.

Like any other oils, fire-resistant fluids degrade in heat and reduce oxidative stability. It is important to note rotating pressure vessel oxidation test (RPVOT) values to ensure your fluid has enough oxidative stability.


Fire-resistant fluids are great options for equipment and environments that are susceptible to fires. If you have high-pressure machines, it is imperative to consider fire-resistant fluids to prevent potential sprays that can ignite. Twin Specialties offers both water glycols and polyol esters to meet your needs. Contact Twin Specialties for product information.

How to Select the Right Grease

Selecting a grease or lubricant is one of the most crucial decisions you make in regards to any machine. Your selection might make the difference between cost savings, reduced downtime, or significant unexpected costs and failures. For oil lubricants, many OEMs specify what product or what type of product is recommended for each component of their equipment. This simplifies the selection process. However, OEM grease specifications are much broader. Most of the time OEMs simply recommend the National Lubrication Grease Institute (NLGI) specification.

This presents both flexibility and options, but also introduces more room erroneous decision-making and poor lubrication. Simply using the NLGI grade is not enough. You have to look at other factors to ensure you grease and machine work properly and does not fail. We will look at some key factors that every operator needs to consider.

Base Oil Viscosity

A grease is composed of 3 ingredients: thickener, oil, and additives. The NLGI number indicates the thickness of the thickener, but does not specify the viscosity of the thickened base oil. The underlying base oil has its own viscosity just like any lubrication oil. If a piece of a equipment calls for a certain lubricating oil with a specific viscosity, it is easy to find a grease that has the same base oil viscosity and similar additive package.

If viscosity requirements are not specified, you can use the chart below (courtesy of ExxonMobil and Noria).

The two factors required are operating temperature and DN or NDm, which are the bearing speed factors. To calculate those speed factors, simply use the following formula:

  • DN = (rpm)*(bearing bore) and
  • NDm = (rpm)*((bearing bore + outside diameter) / 2)

The intersection of DN and Temperature will point you towards the required ISO viscosity. This chart assumes viscosity index.

Base Oil Type and Additives

Once a viscosity is identified, you need to figure out what additives and base oil you need. Similar to oil lubricants you must assess your operations and figure what additives are necessary or unnecessary. For example, light loads and high-speed applications do not require a grease with extreme pressure (EP) additives, but a heavily loaded application will need those EP additives. The chart below breaks down the needed additives for various bearings.

Courtesy of Noria

Most greases use mineral oil and only require mineral oil. However, synthetic base oils are recommended for certain extreme temperature applications. Applications with low or high operating temperatures or a wide range of temperatures, a synthetic base oil is recommended. Synthetic base oil greases are also recommended for users who want to longer regreasing intervals.

Grease Thickener

Unlike lubricating oils, greases include thickeners. The two factors that distinguish grease are type and consistency. As mentioned earlier, consistency is based on the NLGI scale. The scale ranges from 000 (most fluid) to 6 (least fluid). The most common and most recommended NLGI grade is #2. Most OEMs specify the NLGI grade and matching that number is a simple process (especially if you require a NLGI 2 grease).

The other factor for thickeners is the type of thickener. The differences between each type of thickener are present pros and cons for each application. The most common types are lithium soap, lithium complex, and polyurea. Lithium soap greases are low-cost general-purpose grease and perform well in general applications. Lithium complex is similar to lithium soap, but is preferred for applications with higher operating temperatures. Polyurea greases have good high-temperature properties and have high oxidation stability and bleed resistance. When switching greases, it is important to understand thickener compatibility to make sure the new grease does not fail.

Cost and Other Considerations

When purchasing a grease, a basic lithium grease will be cheaper than a sophisticated polyurea grease. It is up to you to determine the tradeoffs between grease costs and performance gains/losses. Purchasing a higher quality grease may lead to longer regreasing intervals and less machine failure.

To save costs, consolidating greases may be wise, but be wary of over-consolidation. This may result in some machines not using an appropriate grease.

Other attributes should be considered depending on the application. Some grease exclusive attributes include:

  • Drop Point
  • Mechanical Stability
  • Water Washout
  • Bleed Characteristics
  • Pumpability

Certain attributes are focused specifically on heavy loads and should be considered for heavy load-low speed applications. These include:

  • Four-Ball Tests
  • Timken OK Load

Additionally, industry specific requirements will also dictate grease selection. These industries have strict requirements and require greases to be certified by certain 3rd-party regulators:


Unlike oils, greases have many more factors for product selection. These factors should be considered for each application as each grease is designed and manufacturer specifically for each application and have a delicate balance of thickener, oil, and additives.

Twin Specialties carries a wide variety of greases to meet you application needs. We work directly with you to make sure we provide the right product that delivers performance while being mindful of the total cost of grease and maintenance. Contact Twin Specialties to learn more about our grease product lines.

A Guide to Base Oil Groups

In any oil-based lubricant the base oil will compose 80-99% of the product you use. What are differences in the main ingredient of your lubricant? The American Petroleum Institute classifies base oils into 5 groups. These classifications are based on the chemical composition of the base oil and the treatment of the base oil.

If a base oil is classified as Group I-III, that base oil will be composed of crude oil that has been treated. The differences depend on the treatment processes applied to the oil.

Petroleum Base Oils

Group I

Group I base oils are the least refined base oil. Two main characteristics of Group I base oils are that they are composed of less than 90% saturates and/or greater than 0.03% sulfur. If either of these conditions are satisfied, then the base oil will be classified as Group I. The only process that is used is solvent refining, which allows Group I base oil products to be cheaper than their more refined equivalents. These are generally used for less-demanding applications and could be ideal for applications where lubricant consumption is high.

Group II

Group II base oils are more refined than Group I. In addition to solvent refining, these oils are also hydrocracked purify the oil. Unlike Group I base oils, these base oils must contain over 90% saturates and less than 0.03%. The greater percentage of saturates gives these lubricants better antioxidation properties than Group I base oils.

Failure to meet either of these requirements will result in a Group I classification. These products also have a viscosity index of 80-120. These oils have good performance in volatility, oxidation stability, wear prevention, and flash point. They only have fair performance in cold temperature environments. Given costs of treatment today, Group II lubricants are most commonly used today and many users have switched from Group I oils to Group II oils.

Unofficially, there is a Group II+ that are composed of high-end Group II base oils. These base oils must have a viscosity index of 110-120 to be considered Group II+.

Group III

Group II base oils must meet the same conditions (saturates and sulfur) as Group II, but also must have a viscosity index greater than 120. These base oils are severely hydrocracked, hydroisomerized, and hydrotreated to crate the best grade of petroleum base oil. These products offer superior stability and molecular uniformity, which makes them ideal for some semi-synthetic lubricants.

Some people consider Group III base oils to be synthetic. The API classifies them as mineral oil since they are derived from crude oil. They do mimic characteristics of synthetic oils including high viscosity indices. A lawsuit between Mobil and Castrol occurred due to Castrol marketing their Syntec lubricant as a synthetic even though it was composed of Group III base oils. In a 1999 ruling, the product was allowed to marketed as a synthetic.

Many people reject the decision and only consider Group IV and Group V base stocks as “synthetic.” Some Group III lubricants outperform Group IV lubricants if they contain excellent anti-wear, anti-oxidant, and other additives. Similar to Group II, Group III base oils have an unofficial Group III+, which consist of Group III oils that have a “Very High Viscosity Index (VHVI).” The VHVI minimum is anywhere between 130-140.

Synthetic Base Oils

Group IV

Group IV base oils are synthetic base oils that composed of polyalphaolefins (PAOs). These products have a viscosity index of 125-200. These base oils are not extracted from crude oil, but made from small uniform molecules. The uniformity and manufacturing of these oils allows for predictable properties that assure performance in tough conditions. These properties include extreme temperature stability, which makes these products ideal for cold and hot weather climates.

Lubricants composed of polyinternalolefins (PIOs) are considered to be in the unofficial Group VI. Similar to PAOs, PIOs use different chemicals in its synthesis process to obtain an even higher viscosity index. Their official API classification would be Group V. Certain food grade lubricants are composed of Group IV PAOs.

Group V

Group V base oils are any base oil that is not classified as a Group I-IV base oil. Common Group V base oils are polyalkylene glycols (PAGs) and various esters. One exception is white oil, which is a very pure lubricant commonly used in cosmetics and food processing. Also used in food grade lubricants, Group V base oils such as PAGs or esters can be used in certain biodegradable base stocks rather than vegetable or seed oils. It is important to note that most PAGs are only compatible with other PAGs.

Key Takeaways

When selecting a lubricant, it is important to understand what base oil is used. Given that the base oil is 80-99% of a lubricant, you should know what base oil you are using. Upgrading the Group III or Group IV could improve performance and reduce consumption. Twin Specialties offers a variety of industrial and specialty lubricants made from a variety of base stocks to meet your operating and budgetary requirements.

What is Viscosity Index?

While researching lubricants, there are many factors to consider in selecting a lubricant: viscosity, flash point, pour point, and oxidation stability. Viscosity is the most important parameter since the viscosity grade can be the difference between optimal performance and machine breakdown. However, the ISO Viscosity Grade (VG) is determined at 40⁰C and will fluctuate depending on operating temperature. Viscosity index is a measure of how much the viscosity will change as temperature rises or falls.

Viscosity Index Explained

Viscosity requirements are based on things such as: component design, loads, and speed. Machine recommendations do not account for operating temperatures and temperature ranges. Therefore, it is imperative to take into account average operating temperature when selecting a viscosity. To account for changing temperatures, the viscosity index was developed to measure viscosity stability as temperatures change. Viscosity index is a unit-less number that is derived by measuring a fluid’s viscosity from 40⁰C to 100⁰C.

The higher the viscosity index, the greater the stability of the lubricants viscosity. As shown in the chart below, the difference in viscosity index could greatly affect lubricant viscosity and performance:

Source: Machinery Lubrication, Noria

As temperatures move towards extreme highs and lows, the difference in Oil A and Oil B is magnified. Oil B, which has a VI of 150, maintains a viscosity closer to its ISO VG of 150 as temperatures rise and fall. On the other hand, Oil A fluctuates much more and could adversely affect performance at extreme temperatures. If your operation will have fluctuating loads, speeds, temperatures, etc., it is imperative to select a lubricant with a higher viscosity index.

Viscosity indexes, which can be found on most product data sheets, typically range from 90 to 160, but can exceed 400 and be as low as -60. The viscosity index can also give insight into the type of base oil and its quality. More refined mineral oils and synthetics will have higher VIs than lower quality base oils. Some products may include viscosity-index improver additives to help stabilize the lubricant in extreme conditions. VI-improver additive molecules adopt a coil shape in cold temperatures and have little effect on viscosity. In higher temperatures, the molecules uncoil and thicken the oil to stabilize viscosity. However, it is important to note that oils with VI-improvers will see permanent loss of VI and viscosity over time.

When Should You Opt for Higher VI

If your operations are going to have variable loads, variable temperatures, variable speeds, and other environmental variables, it is important to select a lubricant with a higher viscosity index. As these variables change, so will the lubricants viscosity. Therefore, it is crucial to invest in a lubricant that will maintain an optimal viscosity across different operating conditions. Conversely, if your operation is fairly consistent, it may suit you to select a lubricant with a lower viscosity index in order to save money.

Some machines may not possess data to identify the optimum viscosity, which could be problematic as ISO viscosity grades are separated by 50% increments between grades (e.g. 46 → 68, 100 → 150). With such large increments, finding the precise optimal viscosity becomes even more difficult. This problem is magnified at lower temperatures, where differences in lubricant viscosity are much larger (as shown in the chart above).

Calculating VI

If you are unsure of a lubricants viscosity or viscosity index, there are online calculators available to help you. If you are unsure of a viscosity index, simply enter the viscosity at two different temperatures and it will return the viscosity index. If you are unsure of a viscosity at a given temperature, enter a known viscosity, known temperature and viscosity index to find the desired temperature to find the new viscosity.

Key Takeaways

In conclusion some of the key reasons to have a lubricant with a higher viscosity index include:

  • Optimal operating viscosity is unknown
  • Varying operating temperatures and/or extreme operating temperatures
  • Other operating variables such as speed and load
  • You want to increase energy efficiency
  • You want to extend oil service and machine service life

Most of these involve improving performance that may be adversely affected by operating uncertainties. In these instances, it is ideal to opt for lubricants with higher VI. In the following instances, using cost-effective lower VI lubricants may prove beneficial to your bottom line:

  • Constant speeds and loads
  • Operating temperature remains the same
  • Optimal viscosity is known and can be consistently reached

If there is more certainty with your operating process, it may not be necessary to invest in a lubricant with a higher VI. It is important to evaluate your operating processes and consult machine manuals to understand your operating conditions. If you are faced with uncertainty and variance in your operations, a higher viscosity index will help smooth operations and increase performance across different loads, speeds, and temperatures.