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Mainly, equipment oils space lubricants designed to be used in gearboxes, transmissions, deliver cases, and other relocating parts of her vehicle. The function of these oil is to protect those parts and helps through the ideal speed.

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The American Petroleum academy (API) explains the properties of gear oils into certain categories prefer GL-4, GL-5, MT-1 etcetera. Amongst all, GL-4 is the most usable one together a lubricant. But can you use GL-5 equipment oil instead of GL4? will certainly it it is in compatible with the engine that uses GL-4 before?

This post will aid you to understand the answers to her questions. Therefore, if you want to know, climate follow the write-up till the end.


What Is A GL-5 equipment Oil?

GL-5 is a kind of lubricant i m sorry is supplied in gear, specifically hypoid gears. That is additionally used in axles operation under various combinations. Climate what room those combinations?

Mainly, the combination is do from various speed and torques conditions. For example, it could be high speed or shock load and also low speed or high torques if girlfriend think around the combinations. The GL-5 gear oils defend the gears and influence the synchronizer so the there will certainly be no trouble while you room riding.

The greater GL rating here method the extreme pressure (EP) will be the a greater level. Still, confused? Well, it way the gears will certainly get greater protection in extreme pressure conditions.

Read our ideal gl-5 gear oil testimonial to know more about it.

What Is A GL-4 gear Oil?

The GL-4 gear oils are used in axles with spiral bevel gearings as a lubricant. These gear oils are renowned for working under middle to serious conditions. It might be speed and load or axles v hypoid gears.

Mainly, the gears operate at reasonable speed and loads. That is why many of the manufacturers pick this form of equipment oil. You deserve to use castle in details manual transmission and also transaxle applications. When the MT-1 lubricants space not suitable to use, for sure you can use the GL-4 equipment oils.

The GL rating is the this gear oil is reduced than the GL-5. That way it will able to provide less protection than GL-5 in excessive pressure conditions.

Can You use GL-5 equipment Oil rather Of GL-4?

Yes, you have the right to use GL-5 equipment oil rather of GL-4. Yet that does not mean you should. The most vital fact here is the API GL rating. You might be reasoning the rating that GL-5 is higher. Then, why are you interrupted from doing it? We space going to discuss broadly so the you can understand why you must not do the replacement.

The Reasons

There space some factors which will protect against you from replacing the GL-4 through GL-5 equipment oil. Right here are some more details around the reasons.

The additive Are based on Sulphur and Phosphorus

The greater GL rating will certainly provide higher EP protection. Therefore, it will certainly need more additives. Mainly, the EP additives room made native Sulphur or Phosphorus compounds. If girlfriend have any kind of knowledge of chemistry, you will indeed worry to hear it. Let us tell you as we take into consideration you execute not know. The nature of this Sulphur or phosphorus-based link is to adhere come the steel surfaces. That is due to the fact that they produce a polar attraction with the metals.

They strike the steel Surfaces

When the EP additive are presented to the metal surfaces, they attach through steel wetting polar attraction. Then the warmth is produced, and the additives attack the metals. This strike is so aggressive the it wears out the synchronizers prematurely.

So which One has actually Fewer Additives but Standard Protection?

Typically, the GL-4 products use additives the have half of the Sulphur and also phosphorus link amount the GL-5 commodities use. It way you will have actually less EP protection. But your synchronizers will certainly be the end of the possibility of getting damaged severely. When you usage the GL-5 gear oil, you will get extra security for the gears. Still, eventually, the synchronizers will acquire damaged.

The synchronizers can wear to the suggest where they cannot make call with the various other side the the cone and also might bottom out before even stopping the the contrary gear.

What room The Difference between GL-4 and GL-5?

Both equipment oils room of the very same categories. Yet what is the difference in between GL-4 and GL-5? let us display you the distinctions with detailed information.

EP Protection

Extreme pressure (EP) defense is defined according to the GL ratings. The ratings are started with GL-1 to GL-6 and also MT-1. As soon as the GL rating is 5, it will give higher protection in extreme problems like speed, loads, and torques. But the GL-4 will administer you with less protection contrasted to GL-5. It will additionally handle less speed and also torque. In high temperatures and pressure, the GL-5 is better. However that does no make that GL-4 as well weak. The maintains legal security to the gears.

EP Additives

The EP additives are one of the crucial differences here. Lock contain Sulphur and phosphorus compounds which are an extremely corrosive. When the equipment produces much heat, the Sulphur and also phosphorus compounds strike the metals. Therefore, it would be ideal to have fewer additives. The GL-4 gear oils contain less amount of these compounds. ~ above the other hand, GL-5 oils have an incredible amount of Sulphur and phosphorus.

Lead Additives

Lead is likewise used in those additive to alleviate the wear in loaded equipment sets. Though command is not an extremely environment friendly, its results will be lessened when you incorporate them with Sulphur and phosphorus. The GL-4 uses less amount the lead contrasted to GL-5.


The viscosity that oil matters as soon as you room using it on your gear. As we know, the GL-4 oils have less 보다 a couple of Sulphur compounds, which helps to minimize the viscosity of the additives. ~ above the other hand, the GL-5 oils have higher viscosity early to much more excellent additives.

Reaction with metal Alloys That used Copper

The GL-5 oils are more active on steels surface once they are made of steel alloys. Periodically copper is offered as one alloying element. The result is devastating when you add oils that have actually a more significant amount that Sulphur. In this category, the GL-4 oils are much less reactive v copper.


The GL-4 gears oil is an ideal when the equipment is hypoid. Castle will give you standard company under severe conditions. Yet the oils are without shock loading. Once it concerns GL-5 gear oils, they will additionally give you an effective service and shock loads. However most the the manufacturer does no recommend to use it in her gearbox.

Can you Mix GL-4 and GL-5?

We would certainly not price negatively. Intend you execute not find any type of GL-4 equipment oils straight or have a less amount the GL-4 oils. Hence, can you mix GL-4 and GL-5 to use in the gearbox? Well, a mixture with GL-5 and GL-4 deserve to be provided in the gearbox. You can additionally use a mixture the MT-1 and also GL-5 come put into the gearbox. However all the engineers recommend not to usage the GL-5 in the engine. Even if girlfriend the mixture with GL-4, there will always be a possibility that it might damage the bronze components in a gearbox.

Therefore, it would certainly be ideal not to use GL-5 in the gearbox, not even the mixtures. This could be applicable just for emergencies once the GL-4 is no being found directly.

Which One Is Better?

The GL-4 equipment oils are better when it concerns using the gears because that a long time without replacement. Native the discussion above, you should know about the additives provided in this oils and also the EP protections. To acquire extra defense in extreme conditions, it will perform a fool’s task to usage GL-5 in the gearbox. The is due to the fact that the Sulphur and phosphorus compound and lead additive will damage the gear’s metal surface and also metal alloys.

The GL-4 oils will not be this corrosive and also will provide you typical protection. There is no a doubt, GL-4 equipment oils are far better than GL-5 oils. Castle are also the right an option if you are concern about the gear’s longevity.

Some final Tips

If you space thinking about using GL-5 gear oil rather of GL-4, you need to know part tips. Very first of all, nobody knows better than the manufacturers that made different species of this oils. Together they made various categories, it will not be way to violate their categories and also interchange the lubricants. One more thing to notification is to remember the properties of every lubricant the you are using in her engine. That should help you in this situations.

Bottom Line

Gear oils are the lubricants that assist with the speed and also loads. They room specified about their practical areas and also their properties.

Hence, can you usage GL-5 equipment oil rather of GL-4? We will not recommend it. That is because you will quickly notice the result if you usage the GL-5 oils. Take treatment of your car if you desire to reap the drive without facing trouble.

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