Gear oil’s job is to smoothen your vehicle’s transmission. Besides, it protects your car’s internal components from wear and tear.
But before using any gear oil, you’ll have to check the GL rating. Higher GL rating indicates that it has more EP protection. However, when you add higher GL-rated gear oil to your engine, it will require more additives.
Some of the common gear oils are GL4 and GL5.
You might be wondering – can I use GL5 gear oil instead of GL4 or vice-versa?
Is there any disadvantage of using these gear oils interchangeably?
If you are confused about this, this blog is for you.
Can I Use GL5 Gear Oil Instead of GL4?
No, it is not recommended to use GL5 instead of GL4 gear oil or the other way around. Because when you add high-rated GL oil to your vehicle’s engine, it will require more additives. But additives contain phosphorous and Sulphur, which can be corrosive to your vehicle’s engine.
GL4 Gear Oil
You can use GL4 gear oil in moderate conditions. Besides, it has the capability to operate at moderate loads and speed. Moreover, you can use GL4 gear oil in transaxle and manual applications. Because of all these, GL4 gear oil is advised by almost every vehicle manufacturer.
GL5 Gear Oil
GL5 is suitable for hypoid gears. Compared to GL4 , GL5 provides more protection in extreme conditions. Besides, it can operate at high speed, torque, and load. However, this gear oil requires more additives, which sometimes can be harmful to the gearbox. Besides, it can decrease the lifespan of the gearbox.
GL4 vs. GL5 Gear Oil
1. Viscosity
While shopping for gear oil, you’ll have to consider the viscosity of the oil. As GL4 gear oil has fewer Sulphur components; it is less viscous. On the other hand, Gl5 gear oil has more Sulphur and phosphorous components, which increases the viscosity of the gear oil.
2. Required Additives
As I mentioned earlier, when you use high-rated gear oil, your vehicle will require more additives. These additives contain Lead, which helps to minimize the wear on the gear parts. However, when you mix Lead with Phosphorous and Sulphur, the effect of Lead will be reduced. Besides, Lead is very toxic and harms the environment.
3. Extreme Pressure Protection
GL rating starts from 1 to 6. When you use higher GL-rated gear oil, it will protect your vehicle from speed, torque, and loads.
Compared to GL5, GL4 will provide you less protection from torque, load, and speed. Besides, when you add GL4 to your gear, it will be able to handle less torque and acceleration. However, it certainly doesn’t indicate that GL5 gear oil is superior to GL4.
4. Reactivity
If you compare GL5 with GL4 gear oil in terms of reactivity, GL4 is less reactive than copper metal. It means it will not damage the copper parts in your vehicle’s gearbox.
5. Additives
GL4 gear oil has fewer Sulphur and Phosphorous additives compared to the GL5 gear oil. But why do we bother about the additives in the gear oils?
When the gearbox becomes hot, these additives, such as Phosphorous and Sulphur, attack the metals of the gear parts and damage the gearbox. This is why it is advised to use gear oil that has less Sulphur or Phosphorous contents.
6. Usage
You should use GL4 gear oil when your vehicle’s gear is hypoid. By adding GL4 gear oil, you’ll get quality service even in extreme conditions. However, you should know that GL4 doesn’t offer shock loading.
On the flip side, GL5 offers quality service with shock loading. However, most car manufacturers don’t recommend using GL5 gear oil in your vehicle.
Who Wins: GL4 or GL5?
If you want to increase the longevity of your vehicle’s gearbox, no doubt, GL4 gear oil will be the best for your vehicle.
As stated above, GL4 gear has fewer Sulphur and phosphorous components. As a result, when the gearbox is heated, Sulphur or phosphorous doesn’t attack the metals. On the flip side, GL5 gear oil has more of these additives, which can cause some serious issues. So, in terms of additives, GL4 is the winner.
However, you may think that GL5 offers more protection in extreme conditions. But it won’ be wise to use GL5 considering its cons.
So, it is safe to say that GL4 gear oil is suitable and will help you increase the longevity of your vehicle’s gearbox.
Frequently Asked Questions about GL4 and GL5 Gear Oil
Most engineers or car experts won’t recommend you mix GL5 gear oil with GL4. Because when you do, it can damage the vehicle gearbox. That’s why you should avoid mixing GL4 gear oil with GL5. However, if you don’t have GL4 nearby, you can mix GL5 with MT1.
GL5 is synthetic gear oil, which has superb thermal oxidation stability. This gear oil is perfect for heavy-duty trucks and industrial machines.
GL5 gear oil has Sulphur and Phosphorous, which can damage the copper, bronze, and brass parts in your vehicle gearbox. That’s why GL5 gear oil is not considered Yellow Safe.
If you drive your vehicle in racing conditions, you must use gear lube in your vehicle’s gearbox. There will be less viscous drag and power loss when you use gear lube. Besides, gear lube has more flow compared to other conventional oils.
Conclusion
Clearly, you should never use GL5 instead of GL4 gear oil. Because it can damage the metal parts in your gearbox. Besides, with GL5, the longevity of the vehicle gearbox can reduce drastically. So, don’t use GL5 and GL4 gear oil interchangeably. And if you really need to add GL5 gear oil, always mix it with Mt1 gear oil. If you are still confusion, contact nearby car mechanic or vehicle expert.
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