What Is the Difference Between Gl4 and Gl5 Gear Oil

You've probably heard of GL4 and GL5 gear oil if you're a car enthusiast. Whether you're changing your vehicle's gear oil for maintenance or upgrading its performance, understanding the differences between these two types of gear oil is critical. The composition, application, and performance of GL4 and GL5 gear oils differ.

In this comprehensive blog post, we'll delve into the six key differences between GL4 and GL5 gear oil and explore whether using GL-5 instead of GL-4 is possible. Furthermore, we'll discuss which one is more common and whether gear oil can go bad with age. So, buckle up and let's jump into the world of GL4 and GL5 gear oil.

What Is The Difference Between Gl4 And Gl5 Gear Oil: 6 Difference

Gear oil GL4 and GL5 have some key differences. Some of them are listed below:

1. EP Additive Levels and Performance

GL-5 gear oils have around twice as many EP additives as GL-4 gear oils to ensure optimal performance in high-speed, high-load applications like modern automotive axles. EP or extreme-pressure additives protect gear systems from wear and tear under heavy loads and high speeds.

These additives form a protective film on the metal surfaces, reducing friction and preventing metal-to-metal contact. As GL-5 gear oils contain a higher concentration of EP additives, they provide enhanced protection and lubrication, making them suitable for demanding applications.

EP additives make GL-5 gear oils more wear, scoring, and pitting resistant so they last longer.

2. Application Scope and Gear Type:

GL-4 gear oils are suitable for manual transmissions with moderate speeds and loads. They work well with spiral bevel and hypoid gears in car axles and spur/helical gears in manual transmissions.

On the other hand, GL-5 gear oils are specifically designed for hypoid gears in automotive axles that are exposed to demanding conditions, such as high-speed operations and heavy loads. If you have a manual transmission with moderate speeds and loads, GL-4 gear oil would be the appropriate choice.

However, GL-5 gear oil is better for hypoid gears in automotive axles subject to high speeds and heavy loads.

3. Protection:

EP additives reduce friction between gear surfaces, improving overall gear performance and efficiency. GL-5 gear oils contain higher levels of EP additives than GL-4, making them suitable for gears subjected to extreme stress.

Increased EP levels in GL-5 gear oils ensure superior protection, especially in high-pressure and high-temperature applications.

4. Compatibility and Limitations:

When using GL-5 gear oil, it's important to know its limitations and potential incompatibility with materials like bronze and copper. The sulfur/phosphorus additives in GL-5 formulations can react negatively with these materials. This reactivity can lead to corrosion and damage, making GL-5 unsuitable for use in gearboxes unless specifically allowed by the manufacturer.

On the other hand, GL-4 gear oils can be a more versatile option in certain applications. They can be used for hypoid gear service under severe conditions without shock loading. This means that GL-4 gear oils can provide enhanced protection without the risk of material incompatibility.

It's important to understand the specific requirements of your machinery and consult with the manufacturer to determine the appropriate gear oil for your needs.

5. Manufacturer Recommendations and Gearbox Suitability:

GL-4 gear oils are typically recommended for moderate-speed and load applications, while GL-5 gear oils are ideal for high-speed and high-load scenarios.

However, it's important to note that GL-5 gear oils may not be suitable for all gearboxes due to potential compatibility issues with certain materials. Therefore, following the manufacturer's recommendations is essential to ensure the correct gear oil is used for the specific gearbox.

Is it possible to use GL-5 instead of GL-4?

Although GL-5 and GL-4 gear oils may seem similar, they are not interchangeable. The main difference lies in each formulation's level of extreme pressure additives. GL-5 gear oils are designed for high-pressure applications and contain a higher concentration of additives to withstand the demands of heavy-duty gearboxes.

On the other hand, GL-4 gear oils have a lower concentration of extreme pressure additives and are suitable for less demanding applications, such as manual transmissions and light-duty gearboxes. The higher concentration of additives in GL-5 gear oil can damage synchronizers and other internal components in gearboxes that require GL-4.

It is always best to consult the manufacturer's specifications to ensure the correct gear oil is used for optimal performance and longevity of the gearbox.

What Is The Most Common Gear Oil Gl-4 Or Gl-5?

Based on the information provided, it is clear that GL-4 is the most common gear oil grade used in synchromesh gearboxes and transaxles. However, it is important to note that GL-5 gear oil is also available and may be used as a substitute for GL-4 in certain applications.

While GL-5 oils contain extreme pressure additives like GL-4 oils, they typically have a higher concentration. This makes GL-5 gear oil more suitable for heavy-duty applications like those found in trucks and SUVs.

Conclusion

As we come to a close, it is important to understand that the choice between GL4 and GL5 gear oil is not as simple as picking one over the other. GL5 gear oil provides better protection under high pressure and temperatures, making it ideal for heavy-duty applications.

Whereas GL4 gear oil is useful for older vehicles and manual transmissions requiring a lower friction modification level. The key takeaway is that it is always best to consult the manufacturer's recommendations before choosing between the two varieties.

Ultimately, the decision between GL4 and GL5 gear oil will depend upon your vehicle's specific needs.