Merlo Tech Talk: Hydraulic Fluid

Merlo Tech Talk: Hydraulic Fluid

The summer solstice usually means temperatures climb for most parts of the USA. It’s these seasonal outside temperatures that affect the inside workings of every Merlo telehandler. There are 7 kinds of fluid a Merlo telehandler will use:

  • Wiper fluid
  • Diesel
  • Def (most machines)
  • Antifreeze
  • Motor Oil
  • Brake Fluid (Dot 4 in case you are wondering)
  • Hydraulic Fluid

Of the list of fluids needed to gain optimal machine performance, the weight, or viscosity, of the hydraulic fluid is important. As the seasons change, the hydraulic fluid weight may need to change also.
If your Merlo is set up to work within a geographical area with temps dipping below freezing (32° F/ 0°C) for days, a thinner 22 weight hydraulic fluid is recommended.
If the machine is working in an area where temps do not dip below freezing for long periods of time, but do stay cold for many days the recommended 32 weight will keep your machine operating at peak performance.
For those areas, such as here in the Piedmont of the Carolinas, where the temps do not get too cold for too long and do not stay too hot for too long, the sweet spot is a 46 weight fluid.

Why the viscosity matters

Hydraulic fluid has one job: supplying lubrication to create the compression needed to keep moving parts moving. The right hydraulic fluid ensures seals, such as the O rings, stay ‘healthy.’
Take the winter season. On a very cold day, if it takes 30 minutes or so for a machine to warm up before it can function, using the 22 weight fluid is the better choice. Thinner hydraulic fluid warms up faster and will remain viable for longer periods of time in colder temps.
When the temperatures are consistently temperate, it is recommended to move to a higher viscosity hydraulic fluid, such as the 32 weight; something that can handle the warmer temps. Consistently hot days will thin out the 22 weight fluid to where it’s more like water, causing the fluid, as well as the parts it lubricates, to wear out faster.
To find the correct hydraulic fluid, that sweet spot, for your Merlo telehandler, pay attention to seasonal temperatures and how the machine operates.
If the fluid needs changing, it is recommended to drain the tank before adding new hydraulic fluid. If the drained fluid does not contain contaminants, it can be stored for use again when the temperature best suits its viscosity. If it does contain contaminants, please dispose of it properly.
Technical questions on Merlo telehandlers can be sent to or contact our team at 803-327-4949.

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