Written By: Corey Foy


We have previously covered the current specifications for Engine Oil (see here) - today we are going to discuss gear oil specifications. The first clarification when discussing gear oil is the difference between industrial or automotive gear sets. These two sets of products have different formulations to ensure protection for different types of gears and applications.

Industrial Gear Oil Specifications

Industrial gear oil requirements can vary depending on the country that the gear sets were manufactured in.

The most common requirements are AGMA 9005/F16 standard which specifies the viscosity and additive requirement of the gear oil.  The current version of AGMA specification has moved to a standardized system recognizing the ISO viscosity as well as additive components when identifying requirements.  For example, an Industrial Gear Oil ISO 150.  Past versions of the AGMA specification would have called this an EP 150 or an AGMA 4 gear lube.

CLP is a German gear oil specification similar to the AGMA standard, but it is used in conjunction with the ISO viscosity scale for identifying requirements.

  • CLP – mineral oil
  • CLP HC – Synthetic polyalphaolefin (PAO) or polyester (POE) oil
  • CLP PG – Synthetic polyglycol (PAG) oil

That means that an owner’s manual may specify a CLP HC 220, which would mean it requires a PAO or POE oil with a viscosity of ISO 220, that contains the correct antiwear formation for industrial gears.

Automotive Gear Oil Specifications

There are two main specifications when dealing with automotive and mobile equipment requirements, and those are API GL-4 and API GL-5.  The major difference between the two specifications is the amount of EP (Extreme Pressure) additives used during formulation.  A GL-4 gear oil has roughly half of the sulfur/phosphorus additive packaged that is contained in a GL-5 gear oil.

API GL-5 products are your 75W90, 80W90, 75W140 styles of products, used in applications with hypoid gears under high speed, shock conditions, or low speed and high torque situations.

API GL-4 products are for spiral bevel gear sets operating under moderate conditions.  You’ll usually find this style of product is a multifunctional fluid such as tractor hydraulic fluid, tractor transmission fluid, or a TO-4 fluid for Caterpillar specifications. GL-4 lubricants have less extreme pressure additives in their formulations, making them safe for the transmissions in off-highway heavy equipment.  You will still want to ensure you have the right product for that type of application though which will most likely need to meet a J20C (John Deere) or TO-4 (Caterpillar) specification as well as the API GL-4.

If you ever have any questions about your oil specifications please call 1.800.463.0354 and speak to our Technical Specialist - Corey Foy.