ISO 46 vs AW 46 Hydraulic Oil: Are ISO And AW Oil The Same?

When you are looking at buying this type of oil, you will run into these two types. While they both do a good job of lubricating machine and heavy equipment parts, they are not necessarily the same. There is a little difference between them.

No, ISO and AW hydraulic oil are not totally the same. They will have similarities as well as the same purpose. But one is held to higher standards than the other, making it a better quality hydraulic oil to use.

To learn more about these two oil types just continue to read our article. It has the information you want to know about so that you know which type of oil is right for your purpose. Even the labels mean different things.

What Does ISO Stand For


Those letters stand for the International Organization for Standardization. It was formed in 1946 in London, and 25 countries met at that time to discuss the issue of standardization.

The letters are actually taken from the Greek word ‘isos’ which means equal. When you see the letters ISO46 on a can of hydraulic fluid, you know that it is the same thing the world over.

The guidelines for international standardizations are updated regularly and if you see ISO 9001: 2015 then that means those guidelines were updated in 2015. This organization does influence the AW products to some extent.

What Does AW Mean?


These letters simply mean Anti-wear. The ISO has a different pair of letters to classify any product with the AW letters on it. Those letters would be HM. The anti-wear products provide protection for heavy equipment and have different levels of viscosity and additives.

While petroleum-based, the AW hydraulic oils have different applications. For example, AW 46 is for off-road heavy equipment, while AW 32 is a weather additive that protects snow plows and other machinery in cold weather.

When you look at the ingredients in these oils you will find the additive zinc dialkyl dithiophosphate, often called —ZDDP. This additive protects the hydraulic pumps.

Are ISO And AW Hydraulic Oil The Same?


The best answer would be yes and no. Technically they are both hydraulic fluids but the AW version has more additives than the ISO version. Then the ISO version of this oil is designed to meet the standards set by the International Organization of Standardization.

That means that the components will be different even though the oils may be used in similar applications. As you read the AW type is an anti-wear hydraulic oil that is designed to protect hydraulic parts working under different conditions.

The SIO type is designed to meet the ISO’s standards for viscosity. That is a difference between these oils. The ISo rating tells you how the oil will flow at any given temperature. The higher the temperature the thicker the oil.

The AW type will be lubricating the different parts like the ISO type, and also has those additives that work hard to protect the parts under extreme stress and heavy use.

Technically, there is a difference between the two types of hydraulic oil and the differences will be in the additives or lack of them.

ISO 46 vs AW 46 Hydraulic Oil

Here is a chart that should help you see what these two labels mean and how they work:

Property ISO hydraulic oil AW hydraulic oil
Viscosity Formulated to meet ISO standards for viscosity. Not subject to viscosity standards
Protection against wear and tear No special additives for extra protection Formulated with special additives for extra protection against wear and tear
Applications Typically used in industrial and mobile equipment Typically used in heavy-duty equipment such as construction and mining machinery.
Operating Temperature and Pressure Suitable for equipment that operates at moderate temperatures and pressures. Suitable for equipment that operates at high temperatures and pressures.
Compatibility Should be compatible with the materials and seals used in the equipment. Should be compatible with the materials and seals used in the equipment.

** table information taken from-

What makes them different is the additives. That provides a slightly different purpose for these two types of hydraulic oils. If the ISO type had the same additives, then it should be equal to the AW type of hydraulic oil.

How To Select The Right Hydraulic Oil For Your Application


Here are some guidelines to help you choose the best hydraulic oil for the type of work and equipment you will be doing and using.

1. Operating Temperature and Pressure- this is not hard to gauge. You should know if your equipment will be operating at a high temperature or a medium temperature level. If it is the former then you will need the AW type of oil.

If it is the latter, then you will need the ISO type of oil. Those divisions include pressures as well. The pressure you put on your equipment will determine how long the parts will last.

2. Protection against wear and tear- where are you working and what will the conditions be while working? If you are working in harsh conditions and have a lot of heavy-duty work to be done, then you would want the AW hydraulic oil protecting your machinery.

If the conditions and work level are not so harsh or heavy, then you will want to go with the ISO type of oil.

3. Viscosity- it is a big word but all it means is the flow rate of the oil at a given temperature. This is very important information to know because some pieces of equipment need a certain flow of oil to operate correctly.

If that is the situation for your workload, then you would be better off using the ISO hydraulic oil.

4. Compatibility- as you see by the chart this category is a bit ambiguous. Each hydraulic oil type is designed to work with specific seals and materials installed in your equipment.

To get this information you need to look up the manufacturer’s specifications for the equipment it made. Use their recommendations so you do not damage any of the internal parts of your equipment.

Can you Mix ISO 46 And AW 46 Hydraulic Oil?


Some people say that ISO 46 and AW 46 hydraulic oil are the same. This may be true in their basic forms., But when you start including additives in the one, then there is a slight difference between the two oils.

Because of those additives, it is not recommended that you mix them. One of the reasons for not mixing is the compatibility factor. One of the two oils may not be safe to use with the materials or seals in some of your heavy equipment.

Another reason would be that the additives may be compromised and not perform as they should. You may lose anti-wear protection if you do combine the two types of oils.

This recommendation goes for the different ISO numbers. For example, you cannot mix ISO 46 with ISO 68. These two oils have different levels of viscosity and they do not mix well. However, you can replace ISO 46 with ISO 68 and vice versa. Just make sure to get all the old out first before adding the new.

What is ISO 46 Equivalent To?

Here is a little table that will show the equivalents of different SAE oils with ISO and AW oils:

SAE oils ISO/AW hydraulic oils
10W 32
15W or 20W 46
20W 68
30W 100

** information taken from-

There has been talk that if you run out of hydraulic oil, you may be able to use some multigrade oils in its place. You would have to look up which types of multigrade oil you can use and when.

When it comes to post-1980 tractors, the hydraulic and transmission systems use the same hydraulic oil. But you need to keep to the specs of your specific tractor as different manufacturers make their tractors use different levels of hydraulic fluid.

Then many hydraulic systems are fluid flexible. You will find that engine oil, automatic transmission fluid, and hydraulic compartment-specific oil all work well in some systems.

You would have to check your owner’s manual of the equipment you own to see any further details or contact the dealer and ask them. Red hydraulic fluid is designed to work with high-performance hydraulics in industrial and heavy-duty applications.

Some Final Words

While oil is not oil and different petroleum products have different applications, you will find that there may be some cross-over. This flexibility is good when you are in a desperate situation, you should stick to the recommended oil for the equipment you own and use.

ISO 46 is technically the same as AW 46 but the additives make the difference. Those additives elevate the AW type of hydraulic levels to being a bit better than the ISO options. It just works better under pressure and harsh conditions.

Leave a Comment: