**4. Conclusions**

In this work, the most recent progress on measuring the adhesion and tackiness of greases with the indentation–retraction approach is presented. In particular, the ability of a grease to adhere to a surface (pull-off force) and to form threads when it is being pulled apart (tackiness) strongly depend on the temperature. However, the influence of temperature is not the same for these two grease characteristics. In addition, it was proved that adhesion is strongly dependent on the holder, which means that this property is system oriented. On the other hand, thread formation does not seem to be influenced; thus, it is more of an intrinsic characteristic of the grease. As a follow-up, the influence of other environmental factors such as humidity and material composition will be investigated.

For this method to move towards standardisation, its repeatability and reproducibility should be addressed. From an internal round robin exercise, it was found that the repeatability of the method for one group of measurements (one module, one tester and one grease) is in the range of 5–15%. A similar fluctuation was found between the different modules for the same grease and user, as well as between different users for the same grease and module. From the authors' point of view, this indicates that the method is quite repeatable and reproducible and that the fluctuation is possibly due to the heterogeneous and complex grease structure. However, to draw safe conclusions, a more extended round robin is underway between different labs and well-defined and formulated greases. Another possibility of this method, apart from grease formulation and development, can also be grease condition monitoring.

**Author Contributions:** Tester development, O.M. and M.C.; testing, E.P.G., D.D. and M.D.B.; data analysis, E.P.G., D.D. and M.A.; writing, E.P.G. and D.D.; review, M.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
