When choosing a silicone oil, you’ll often come across different viscosities such as 100 cSt, 350 cSt, 1000 cSt and 5000 cSt. But what exactly does that mean? And more importantly: which one do you need?
In this blog, we’ll explain it for you.

What does viscosity mean?

Viscosity indicates how fluid or viscous an oil is.

* Low viscosity (e.g. 100 cSt) → thin and flows easily (like water)
* High viscosity (e.g. 5000 cSt) → thick and flows slowly (like syrup)

The unit cSt (centistokes) is the standard used to measure this fluidity. The higher the value, the thicker the oil.



Overview of the different viscosities

Viscosity   Feel   Typical behaviour
100 cSt Thin Penetrates well, little resistance
350 cSt Medium Good balance
1000 cSt Thick More cushioning, stays in place better
5000 cSt  Very thick Strong cushioning, almost gel-like


What viscosity do you need?

The right choice depends entirely on your application.

✔️ For light lubrication

Use a low viscosity (100–350 cSt)
These oils ensure smooth movement with minimal resistance.

Applications:

  • Small mechanical parts
  • O-rings
  • Fine moving parts


✔️ For general use

Choose a medium viscosity (350–1000 cSt)
This is the best option if you want both lubrication and durability.

Applications:

  • Household appliances
  • Plastic parts
  • General maintenance


✔️ For damping and controlled movement

Opt for a higher viscosity (1000–5000 cSt)
These oils slow down movement and provide greater control.

Applications:

  • Soft-close systems
  • Shock absorption
  • Precision applications


✔️ For maximum resistance

Use 5000 cSt
Ideal when movement needs to be deliberately slow and controlled.

Applications:

  • Humidity control instruments and humidity meters
  • Level monitoring equipment and level gauges
  • Underwater robotics and ROV technologies
  • Equipment with digital displays


Comparison of viscosity classification systems