OEMs are challenged today to meet the often conflicting demands: government regulations are dictating better fuel economy, while vehicle owners are demanding increased axle durability and performance.

Formulating an automotive gear oil for a particular application requires an in-depth understanding of the relationships between fluid characteristics and axle design. Getting just the right blend of base fluid, performance additives and viscosity modifier performance involves a delicate balancing act to ensure both efficient operation and long equipment life.

Industry performance standards assure that gear oils meet the challenges of different vehicle types. The continuous development of industry specifications means that there are many specification numbers in the market today, but there are four primary specifications for automotive gear lubricants:

  • SAE J306
  • API MT-1
  • API GL-5
  • SAE J2360

SAE J306

The SAE J306 Standard defines automotive gear, axle and manual transmission lubricants in terms of their rheological properties. There are two key elements of the SAE J306:

  • Viscosity identification and labeling guidelines of an automotive gear lubricant: this is important because it establishes a consistent worldwide vocabulary for viscosity grades: 70W, 75W, 80W, 85W, 80, 85, 90, 110, 140, 190, and 250 (SAE 110 and SAE 190 were added in 2005).
  • Shear stability requirements: this is important to enable the use of wide-span multi-grades; in order to ensure the lubricant maintains adequate film thickness to provide equipment protection, shear stability is imperative.  

API Category MT-1

NOTE: this specification is for gear oils used in manual transmissions

In 1986, the SAE outlined the trucking industry's need for a gear lubricant category that would provide performance characteristics essential to ensure optimum service life for heavy-duty non-synchronized manual transmissions. It was determined the class of oils used in manual transmissions was not always in compliance with the builder's primary recommendations. At times engine oils were used in manual transmissions due to availability and convenience.

API Category MT-1 was developed to satisfy OEM objectives for optimum transmission performance and service life. This was achieved by developing a single lubricant that combined the cleanliness and oil seal life typical of engine oils with the load characteristics of gear oils. API Category MT-1 gear oils are used in non-synchronized heavy duty manual transmissions; in these applications a ""double-clutch"" shift is required to change gears.

API Category GL-5

API GL-5 is for gears, particularly hypoid gears in automotive axles under high-speed and/or low-speed, high-torque conditions. The performance specifications of API GL-5 are detailed in ASTM D7450. Lubricants qualified under U.S. Military specification MIL-L-2105D (formerly MIL-L-2105C), MIL-PRF-2105E and SAE J2360 satisfy the requirements of the API GL-5 service designation.

More and more, end-users worldwide are finding that the performance defined by API GL-5 is the practical minimum to deliver acceptable performance and equipment dependability. As a result, API GL-5 may be regarded as the industry's fundamental building block in growing numbers of the world's regions.

SAE J2360

By far the premier standard in common use today, SAE J2360 is a global quality standard specified by many North American OEMs and by growing numbers elsewhere in the world. The rigorous approval requirements, including controlled field testing and independent committee review, ensure that products approved under the SAE J2360 Standard meet the very highest demands of axles. 

Ask the Right Questions

Getting the kind of vehicle performance you expect begins with asking the right questions - and getting the right answers - about lubricant products. Here are a few to ask your supplier.

  • Does my lubricant provide the level of performance recommended by the equipment manufacturer for the type of service I need?
  • What tests were used to evaluate this lubricant, and what relevance do these tests have to my equipment and/or its operation?
  • Why do I need to worry about the ""level of performance"" of my lubricant? I'm using an SAE 80W-90 grade oil, just like my OEM recommends. Doesn't my SAE 80W-90 oil provide all the performance I need?
  • Would my equipment perform better or last longer if I used a better-quality lubricant?
  • Can you provide test data to confirm that the lubricant I'm buying meets the performance requirements that you claim? How can I be sure that the test data is legitimate?
  • May I see the Qualification Number and Qualified Products List for this product? (For products approved under the SAE J2360 Standard)