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    Driving Innovation - Automotive Lubricants

    Driveline fluids are responsible with transferring power through several automotive components and systems.  With so much variety in the make/model of transmissions and gearboxes, how do you formulate the best fluid for the application?  Afton seeks to answer the most common questions surrounding driveline fluids and provide best-in-class additive technology to meet today and tomorrow's performance needs.  
     

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What is a Driveline Lubricant? 

A Driveline Lubricant is a specialized solution of base oil and performance additives to help optimize and protect power transmission in automobiles and heavy-duty equipment.Depending on the engine or transmission type, a driveline lubricant can be engineered to tailor fit the application for optimal performance and protection.There are a few Driveline Lubricant Fluid Types that we will highlight in this article:

  • Transmission Fluids
  • Axle & Gear Lubricants
  • Off Road Fluids

What is a Transmission Oil? 

The transmission in an automotive system is a device connected to the back of the engine that sends power to the drive wheels.  It is an integral part of the automobile responsible for transferring power generated from the engine into forward movement.  A transmission fluid is tasked with protecting critical gears and metal surfaces and ensuring the RPM speed stays within the desired operational range.

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What Goes Into a Driveline Lubricant? 

Driveline lubricant formulation can vary greatly by the specific end application, but all of the fluids can be broken down by three major components, Base Oils, Performance Additive Package, and Viscosity Index Improver (VII).

Component
TypeTypical Composition
(Vol %)
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Base OilGroup I, II, III or IV80 — 90%
Viscosity Index ImproverVII (OCP, PMA)5 – 15%
Additive Package
  • Dispersants
  • Extreme Pressure, Anti-wear
  • Seal Swell Agents
  • Friction Modifiers
  • Foam Inhibitors
  • Corrosion & Oxidation Inhibitors
5 – 10%

Driveline Composition - Base Oil

There are four common base oil types used in the formulation of driveline fluids, each has its own performance properties, benefits and weaknesses to consider. The table below helps simplify the base stock options:

    Base Oil Group
    Group I
    Group II
    Group III
    Group IV
    Sulfur Content (Vol %)
    80 - 119
    80 - 119
    ≥ 120
    140
    Viscosity Index
    ≥ 0.03
    ≤ 0.03
    ≤ 0.03
    0
    Aromatics Content (Vol %)
    15 - 35
    < 10
    < 5
    0
    Characteristics
     - - 
    - - 
     - -
    - - 
    Low Temperature
    OK
    Better
    Even Better
    Best
    Oxidative Stability
    OK
    Better
    Even Better
    Best
    Seal Compatability 
    Best
    Better
    OK
    Poor

Driveline Composition - Viscosity Index Improver (VII)

Viscosity Index Improvers (VII’s) are critical in ensuring consistent lubricant performance across a broad temperature range.  VII’s are designed to dissolve directly into the base oil and expand at higher temperatures to maintain a target viscosity to avoid “thinning-out” and losing the desired protective properties of the oil.  VII’s also contract at lower temperatures to maintain flowability for cold start environments. Afton Chemical provides several options for VII selection in their HiTEC® Performance Additive product line.

Driveline Composition - Additive Packages

There are many different types of performance additive technologies that can be used in a variety of driveline lubricants.  The following table breaks down the most common additive types and the benefits exhibited in final fluid performance.

    Additive Type
    Performance Benefit in Lubricant
    DetergentsAbsorbs and dissolves deposit formation into the fluid to provide cleaner and longer-lasting lubricant performance.
    AntioxidantKeeps the fluid from oxidizing and degrading into potentially harmful and damaging by-products.
    Pour Point Depressant (PPD)Prevents wax crystal formation and inter-molecular bonding at low temperatures that prevents fluid flow & lubrication. 
    Friction Modifier (FM)Reduces overall friction and helps minimize noise, vibration, and harshness (chatter, squeak) experienced that can lead to micro-pitting damage.
    Extreme Pressure / Antiwear (EP/AW) Prevents metal-on-metal abrasion, wear & damage under extreme pressures and high speeds during engine operation.
    Corrosion Inhibitor (CI) Prevents metal surfaces from rust & oxidation that can cause flaking and metal contamination to disperse into the lubricant damaging equipment during operation.
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What Causes a Driveline to Fail? 

There are many potential mechanical root causes for a driveline failure, however there are 3 main causes of failure that can be attributed to the fluid itself.
 

  • Contamination - If the fluid gets contaminated it can lead to premature wear patterns, leakage and ultimately seizure and complete failure. 

  • Incorrect Lubricant Selection - If the lubricant selected does not meet the recommendations of the manufacturer, it may fail to protect the driveline at its operational conditions.  Causing metal wear, grinding and can lead to leakage of the fluid and failure of the component.

  • Not Following Drain Intervals – If the lubricant is not changed out periodically based on the owner’s manual, the lubricant can degrade over time.  This unchanged fluid is subject to potential sludging and deposit formation that can detrimental to the lubricant’s ability to protect metal surfaces and the overall efficiency of the vehicle. 

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What are the Challenges Faced by Driveline Lubricants?

Driveline lubricants are subject to many difficult tasks in an ever-changing environment.  There are a few specific challenges that stand out as most important to keep in mind over the next several years:
 

  • Fuel Economy - The industry standard is to maximize fuel economy and efficiency of new vehicles.  This puts additional burden on automotive lubricants to continue to protect mechanical components with a decreasing fluid viscosity target.

  • Shear Stable Requirements - Multi-grade automotive lubricants include varying amounts of Viscosity Index Improver (VII) that is subject to high mechanical stress and repeated shear.  Overtime this high amount of stress can result in an overall reduction of the fluid viscosity, resulting in a thin, inefficient lubricant.  Performance additives will need to provide higher shear stability and withstand heavy-duty mechanical stresses.

  • Cold Start Requirements – Thermal stability is critical in ensuring engine components are not damaged when transitioning from extreme cold to operating temperatures. As fluid volumes decrease in new engine designs, it is important that these lubricants withstand the environmental conditions and maintain a protective lubrication boundary.

  • Industry Specifications – There are many industry and OEM standard specifications that ensure lubricant performance protects newer equipment designs.  Common Specifications include DEXRON, MERCON, Type-F and more.  If you have industry specifications required for your fluid, Afton & ChemPoint are here to help ensure your formula meets or exceeds those minimum performance benchmarks.

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