Thermal Grizzly Duronaut Thermal Paste Review - Kryonaut was yesterday, welcome to the top 10 of all pastes! (2025)

Application and viscosity

Thermal Grizzly Duronaut is a thermal paste that is characterized by its relatively high viscosity. Compared to thinner pastes, it requires a little more sensitivity and skill when applying, as it is more viscous and does not flow over the surface by itself. However, this consistency has the advantage that the paste remains in place after application and does not escape uncontrollably from the contact area between the processor and the heat sink, which is particularly advantageous in the case of tight tolerances.

To facilitate spreading, it can be helpful to heat the paste slightly. Heating the paste makes it more pliable, which makes it easier to spread evenly over the surface. The reason for this lies in the physical properties of the base materials of the paste: as the temperature rises, the internal friction decreases, making it easier to move the particles in the paste. This leads to better adaptation to microscopic unevenness of the contact surfaces, which ultimately optimizes heat transfer. Slight heating can be achieved by heating the paste to around 40 to 50 °C for a few minutes and minimally heating the target surface, such as the heat spreader and the IHS or the die (hot air dryer).

This not only makes application easier, but also ensures that the paste forms as thin and even a layer as possible, which is crucial for efficient heat conduction. This is exactly why I first wanted to know how far you can go with normal pressure and how much the paste can still be pressed together without destroying anything. For the final pressing, I then use the usual pressures at a constant 60°C median temperature of the paste layer.

Chart comparisons

The paste can be compressed very far, which is important. A thermal paste can deliver better results on a CPU if it can penetrate the micro-roughness of the contact surfaces between the CPU and heat sink more easily due to its consistency. This leads to better initial contact and reduces the thermal resistance at the interface. Layer thicknesses of less than 25 µm are suitable for this purpose if the surfaces are not too curved or rough.

The effective thermal resistances Rth_{, eff}

Now we compare the pastes and only look at the effective thermal resistance. Of course, we also see here how the paste behaves under pressure and at the technically possible BLT. The Thermal Grizzly Duronaut is positioned at the absolute top below 50 µm, so you can only be amazed and I would like to refer you once again to the title of the article in this context. However, the paste remains quite performant even at higher layer thicknesses and is always at the forefront.

I have now compared the relevant layer thicknesses from 25 to 400 µm as a bar chart for _Rth. The Thermal Grizzly Duronaut is also doing well here:

Interface Resistance

What I have already mentioned is the contact resistance, in our case the interface resistance. Here you can see how well the surface of the material “clings” to the contact surfaces (IHS, heatsink). These values are also easily comparable and meaningful, as they are always the same calibrated reference blocks. At around 4.4 mm²K/W, the paste is in the very good mid-range and shows what it can do.

I have already explained in detail how to determine this value in the linked basics, so I won’t go into that here. But it is the value that can have a major impact with very low BLT.

Effective thermal conductivity

Once again, we see how the values change over the BLT, although we can no longer expect a linear curve here due to the included area and BLT. However, the whole thing corresponds well in terms of position with the values for thermal resistance, where the Thermal Grizzly Duronaut is always in the lead and only loses a few places as the BLT increases.

Of course, the whole thing is also available as a bar chart for the most important layer thicknesses. Just click through and see where the paste is positioned:

Apart from the fact that I also have the temperatures of the heater and the water, which are of no use to us because they either adapt to the resistances or always remain constant, I have my measurement setup with the temperature sensors 1 to 6 (see basic article). With these values, you can now also make some very nice considerations.

GPU simulation

Let’s first take the values that show the two temperatures at the respective contact surfaces between which the paste is located and form a delta. These curves are no longer completely linear, as the interface resistance also changes a little. And we no longer calculate with 6 points, but only with 2 absolute values for the temperature difference instead of a gradient as with_TTim, whereby the sample temperature remains constant. And what is the point of all this? The behavior is similar to that of a graphics card, which has to manage without an IHS and where the delta is usually measured between the substrate and the water temperature.

CPU simulation

If we normalize the values for the heater, we already have sufficient thermal resistance in the copper reference block to simulate the CPU temperature and its differences with different pads in comparison with each other and in relation to the thickness of the paste replacement. It is precisely this variable evaluation that no test on a CPU can offer, because the respective CPUs are bent differently and it is therefore not really reproducible. But in the TIMA5 test it is, because I can measure all distances, which is simply not possible on a single CPU.

Interim conclusion

The Thermal Grizzly Duronaut leaves a solid impression overall and proves to be a high-performance thermal paste in the top field. It doesn’t quite reach the level of the DOWSIL TC-5888, which is in a league of its own in terms of thermal conductivity and consistency, but is already EOL. Nevertheless, the Duronaut offers a truly convincing performance that makes it attractive for many applications. Especially in direct comparison to the DOWSIL TC-5550, the strength of the Duronaut becomes clear: it noticeably outperforms the TC-5550 in terms of thermal conductivity in thin layers and thus ensures better temperatures under load.

The TC-5550 is characterized by its extremely durable matrix, making it a reliable choice for applications where longevity and structural stability are paramount. However, this feature raises the legitimate question of whether such a robust matrix on a CPU is really necessary. CPUs are not usually subjected to the same mechanical stresses as industrial components, transmission towers or server processors that run continuously. Here, the longer durability of the TC-5550 could be an advantage, but if the thermal performance cannot keep up, the disadvantages may outweigh the advantages.

For users who primarily value good heat dissipation and stable temperatures under high loads, the Thermal Grizzly Duronaut offers a balanced solution. It combines solid thermal performance with sufficient durability, without the compromises in thermal conductivity that can be observed with the TC-5550. This makes it an interesting alternative, especially for users looking for a balance between performance and longevity without having to commit to the more expensive high-end pastes such as the TC-5888. But more on that in a moment