As we discussed in our last article on SAE J306, this standard is critical when it comes to improving efficiency across all parts of the vehicle. Here, we will take a more in-depth look at this recently-updated standard.
Defining SAE J306 Lubricants
Under the SAE J306 standard, lubricants are defined in terms of a grade denoting their minimum The measurement of a fluid's resistance to flow under the force of gravity at a specific temperature, usually 40°C or 100°C. at 100˚C, as measured according to American Society for Testing and Materials. An organization that develops international standards for industry, including test methods, specifications, and best practices. Many tests that certify a lubricant to a specification are overseen by ASTM. D445, while also demonstrating shear stability as measured by CEC L-45-A99—more commonly known as KRL Shear. This test determines the permanent shear loss of the fluid after 20 hours in a cylindrical roller bearing tester. Wide-span multigrade lubricants typically use performance polymers that are susceptible to shear and if a fluid shears quickly and excessively there is potential for accelerated equipment wear or Cracking, flaking, or spalling of a surface due to stresses beyond the endurance limit of the material.. To comply with the SAE J306 Standard, the lubricant must “stay in grade” after shear to maintain the appropriate level of protection.
Some lubricants are further designated with the letter “W,” for Winter, signifying a low-temperature A measure of a fluid's resistance to flow. A fluid with a higher viscosity flows less easily. grade. In addition to their high-temperature definition, these “W” grades are further defined as providing a maximum temperature—ranging from -12 to -55˚C—at which they retain a threshold level of viscosity.
Balancing Blends for Performance
Achieving the optimal lubricant for a given driveline application requires a thorough understanding of both the equipment application and the properties of the base fluid and additive package. Even for a comparatively simple SAE J306-compliant monograde lubricant, performance additives will be used. The additive formulation needs to reduce The resistance to motion of one object over another. Friction depends on the smoothness of the contacting surfaces, as well as the force with which they are pressed together. and remove heat, and will include extreme pressure and anti-wear additives to prevent wear and other types of distress that can result in equipment failure and downtime. Protection against A reaction occurring when oxygen attacks petroleum fluids. Oxidation is accelerated by heat, light, metal catalysts, and the presence of water, acids, or solid contaminants. Oxidation leads to increased viscosity and deposit formation., thermal degradation, rust, copper corrosion and foaming also must be provided.
The viscosity of lubricants tends to decrease with increasing operating temperature:
- At elevated temperatures, the liquid becomes increasingly thin, providing a lower level of protection.
- Conversely, at lower temperatures the fluid thickens and the increased viscosity reduces the efficiency of the equipment it is protecting. For a driveline required to operate only at moderate temperatures, a monograde product may provide adequate protection at an optimal price point.
However, for operation across wider temperature extremes, a multigrade fluid engineered for a more balanced viscosity profile is required. To achieve the required performance, multigrade fluids need additional additive components. Depending on the extent of cold-temperature operation, multigrade lubricants will, for example, require the addition of a PPD. A lubricant additive that lowers the lowest point at which a lubricant flows so that the lubricant can be used in cold environments. PPDs are typically not included in a performance additive package., and for optimal efficiency, additional performance polymer.
Importance of Pour Point Depressants and Performance Polymers
In cold temperatures, the wax in The primary or underlying fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants. tends to separate out and form crystals that interlock and lead to fluid thickening. As the fluid drops below the pour point, this thickening increases significantly, leading to increased mechanical losses in the equipment as well as reduced lubricant effectiveness. Pour point depressants modify the shape of the wax crystals that form at low temperature, preventing them from interlocking and thus reducing the pour point by as much as 40˚C.
The selection of the correct pour point depressant will be influenced by the choice of base oil, the potential interaction with the performance additive package and any performance polymer used, along with the performance requirements and operating environment of the equipment.
The performance polymer must also be selected to ensure compatibility with the other lubricant components. For many specific applications, a range of polymer structures have been developed to provide the desired performance. Selection of the right product for the right application is crucial in order to avoid compromising equipment performance and durability.
For more information on SAE J306, contact your Lubrizol representative.