Hydraulic oil is the lifeblood of your log splitter. It’s used to transfer power from the engine to the ram mechanism that exerts force on the splitting wedge. 

Choosing the correct type of hydraulic oil for your log splitter is important to ensure optimal performance and prolong its longevity. JAK Max supplies high-quality oil designed to do just that.

Understanding Hydraulic Oil

The main function of hydraulic oil is to channel the engine’s power to the functional moving parts of the equipment. It can do this because it’s non-compressible, so it doesn’t absorb any of the power during transferral. It transmits all the force to the intended destination. 

A log splitter is a simple example of this. It uses a hydraulic cylinder to drive a sharp wedge into the log. Hydraulic oil is pumped under pressure into the cylinder, reaching a hydraulic valve. This valve controls the amount of power, which in turn controls the force that the cylinder exerts on the wood. 

Types of Hydraulic Oil for Log Splitters

Viscosity is the key feature of hydraulic oil. The more viscous the oil, the harder it is to compress, and it takes longer to flow through the log splitter’s cylinder. Thinner oil has a lower viscosity, making it faster and easier to compress.

Hydraulic oil grading

The ISO grading of an oil describes its viscosity. There are two grades suitable for use in your log splitter:

  • ISO 32 – a thin, light oil with low viscosity, best suited for cold environments.
  • ISO 46 – a thicker oil that works well in temperate climates and in hotter conditions.

The AW grading means that the oil contains anti-wear agents and other additives. Thus, you get AW-32 and AW-36 oil. The number indicates the ISO grade and the letters that it has anti-rust additives, for example.

What Weight of Hydraulic Oil Goes in a Log Splitter?

Oil weight is measured based on the oil’s rate of flow at 100 degrees Celsius. Higher viscosity oil has a higher weight factor, which means that it takes longer to flow around the machine’s system after start-up.

ISO-32 and AW-32 are 10-weight fluids, with a low viscosity index of 10 at cold temperatures.

ISO-46 and AW-46 oils are 20-weight fluids, which provide better performance and engine protection at higher temperatures. 

What is the Difference Between AW-32 and AW-46 Log Splitter Oil?

As we’ve explained, the basic difference between AW-32 and AW-46 hydraulic oil is its viscosity. Neither is better; it merely depends on the operating conditions. 

If the viscosity is too high for the conditions, the oil won’t flow properly, particularly with a cold start. On the other hand, if the viscosity is too low in hot conditions, the oil won’t maintain the desired hydraulic force, and won’t provide enough lubrication.

In general, use AW-32 in colder temperatures, as it’s thinner and more free-flowing. Use AW-46 when the weather is hotter.

Anti-wear additives

As the prefix indicates, both grades contain anti-wear ingredients. The difference is that the thicker AW-46 oil has a higher ratio of oil to additives.

In both grades, the additives give a number of benefits:

  • Anti-wear properties help to prolong your log splitter’s lifespan.
  • Anti-foaming abilities prevent bubbles that can compromise hydraulic efficiency.
  • Anti-rust additives protect the metal parts.
  • Anti-oxidants reduce sludge build-up, resulting in less frequent oil changes.
  • Cold flow additives improves oil performance on cold days.

JAKMax hydraulic oil is formulated with rust-prevention additives, oxidation and foam inhibitors, and low-zinc anti-wear properties. It offers superior thermal stability, and prevents sludge formation.

What is the Difference Between ISO-32 and ISO-46 Hydraulic Oil?

ISO-32 hydraulic oil differs from ISO-46 oil in the same way as the AW-grade oils do. The ISO prefix is merely used to indicate that the oil does not contain anti-wear additives.

When it comes to using your log splitter, ISO-32 is best for cold weather usage. Because of its lower viscosity, it’s less resistant to starting up in low temperatures. 

The size of your log splitter also plays a role in your choice of hydraulic oil. While all log splitters are rated for the same pressure, usually 2,500 PSI, larger ones have bigger gears, allowing the machine to generate more force at this pressure. Bigger gears enable more fluid flow, which makes the heavier ISO-46 oil more viable. Stick to ISO-32 if you have a smaller log splitter.

Can You Mix ISO-46 and AW-46 Hydraulic Oil?

As discussed, the only difference between ISO-46 and AW-46 oils is that the latter contains anti-wear additives. They have the same viscosity and weight rating. It’s not usually a good idea to mix the oil in your log splitter, but you won’t damage it if you mix ISO-46 with AW-46. The trade-off is that the presence of ISO-46 means you’ll have fewer anti-wear additives in your oil mixture.

However, you shouldn’t mix different oil grades, like ISO-46 and AW-32, or AW-32 with AW-46. That’s because of the difference in viscosity, which can affect operational efficiency.

Can you mix different brands of hydraulic fluid? Yes, as long as the grading remains the same. Ideally though, you should stick to one high-quality brand like JAK Max, to be sure that you get optimal performance.

What Can I Use Instead of ISO-46 Hydraulic Oil?

It’s quite common to replace either ISO-46 oil with engine oils that have the lowest API rating. You can use SAE-20 rather than ISO-46, as they have the same 20-weight grade.

Hydraulic Oil Maintenance

Because hydraulic oil provides the actual log splitting power, it’s important that you maintain it properly. You should check it regularly, ensuring that you have the right level of fluid.

Other considerations:

  • Oil filters – change these regularly to prevent the oil from losing efficiency due to contaminants.
  • Seals – check for worn seals, which will degrade performance and compromise the pressure of the hydraulic system.
  • Breather caps – keep these clean and unobstructed.
  • Hydraulic lines – too much pressure in the log splitter cylinder can dilate the hydraulic lines, which will then allow too much high-pressure oil through, damaging the seals.

JAK Max Conclusion

Using the right hydraulic oil and maintaining it are properly crucial elements of operating your log splitter. Remember to use lower viscosity ISO-32 or AW-32 oil for cold conditions, then drain and replace it with higher weight ISO-46 or AW-46 in hotter temperatures.

You need look no further than JAK Max hydraulic oil. Our high-performance oils with anti-wear properties will help keep your equipment working smoothly and effectively. They offer superior filterability and oxidation stability, and provide pump wear protection in wet and dry conditions.

Hydraulic Oil FAQs

Which hydraulic oil is thicker – 32 or 46?

46-grade oil is the thicker of the two, more suitable for hot weather operation.

Can you use any hydraulic fluid in a wood splitter?

You should only use the hydraulic fluid recommended in your log splitter’s user manual. Using the wrong oil can compromise performance and damage your equipment.

How often should I change the hydraulic fluid in a log splitter?

Follow a regular oil change routine, depending on how often you use your log splitter. Make sure to inspect fluid levels each time before you fire it up.