Executive Summary
The majority of TLT readers report that new industrial applications such as electric vehicles (EVs) and renewable energy systems have increased demand for novel lubricant formulations. A common challenge readers identify is the gap between laboratory test conditions and real-world applications, particularly as emerging technologies push beyond the limits of traditional test methods. Innovations such as electrified tribometers, multi-sensor data acquisition and advanced surface characterization are key tools in helping to close that gap.

Q.1. Please describe a recent challenge you encountered when developing or testing lubricants for new or emerging industrial applications.
 
Reliability of results.

One of the main challenges we encountered is related to the use of low-viscosity e-fluids in high-speed EV gear systems. While these fluids improve efficiency, they significantly reduce lubricant film thickness, especially under high sliding-to-rolling ratio (SRR) conditions. This leads to increased risk of micropitting and scuffing, particularly in localized contact regions. Another key difficulty is the mismatch between laboratory-scale tribological tests and real gear operating conditions. Standard tribometers often fail to capture transient thermal effects, surface roughness evolution and lubricant starvation observed in actual gear contacts. Bridging this gap between simplified tests and system-level performance remains a critical challenge.

The lack of any agreed-upon testing methods for biofuel contaminated oils and erosion/wear effects of nano-particles as additives.

It is sometimes challenging to match the exact setting, temperatures and materials for certain specialty manufacturing procedures. Lab trials don’t always align with field trial data.
 
A typical challenge is establishing performance criteria to formulate to. Specific tests require modification of the formula to encompass performance and long-term shelf stability.

Lubricants used in electric drives and/or wind turbines are often prone to electric fields and stray currents. They must have a certain dielectric strength while being tribologically stable under varying operating conditions.

We have some solubility and stability issues with S-containing additives in mineral oil-based lubricants, and we are also looking for labs that offer fast, comprehensive sulfur content analysis.

Testers have not caught up to emerging applications, so I have to go to the old basic testers and then extrapolate data. This is not a tribological issue, but it does make a lot of work to explain the finer points to the customers.

Flow or behavior of grease in/around the contact area. Cavitation pressure in textured surfaces.

A recent challenge involved supporting lubricant selection and validation for newer industrial and marine applications operating under evolving decarbonization and environmental regulations. The primary issue was ensuring that environmentally acceptable or lower-emission formulations could deliver equivalent or superior performance compared to conventional lubricants. From a technical standpoint, challenges included managing oxidation stability, additive compatibility and deposit control, particularly when using alternative base oils or reformulated additive systems. Laboratory results did not always fully correlate with field performance, especially under variable load conditions and extended service intervals. Another key constraint was the lack of long-term performance data for these newer formulations, which required a more cautious and data-driven approach involving staged field trials, oil analysis and continuous performance monitoring.

Traditional testing like four-ball, Timken, etc., are not correlating to any known lubricated component or mechanism. It is frustrating to see knowledgeable people debating about these results higher or lower when they say nothing about the real application of the lubricant.

The need to understand fluid conductivity under varying environmental and operating conditions (cannot go into too much detail here).

A key challenge was replicating real electrical loading (voltage/current) alongside mechanical contact during lubricant testing. Conventional tribometers don’t capture effects like electrical discharge damage.

Nothing new.

High temperature stability.

A key recent challenge has been isolating true rolling contact fatigue behavior from corrosion and film-instability driven surface damage when evaluating novel lubricants on steels under low-viscosity, mixed lubrication conditions.

The biggest challenge with developing a test method or testing lubricants for a particular industrial application (especially for an emerging industrial application) is obtaining representative specimens for the contacting surfaces. There are many factors that must be taken into account that will affect the validity of the results. For instance, the macroscopic contact geometry between the two surfaces is perhaps the greatest factor especially with mixed-film and boundary contact. Other factors that are critical are the material and surface roughness properties of the two surfaces. Effect of lubricant additive (i.e., finding optimal concentration of the additive or base oil variety) can be difficult to compare since viscosity effects often mask more subtle effects. A sensitivity analysis is essential before you decide on test parameters. Test parameters for a new application will probably require extensive testing to produce results that correlate with real-world experience. The difficulty is that protection against long-term effects such as wear or corrosion are impossible without a history this is where the sensitivity analysis can be helpful in predicting behavior in adverse conditions.

I’m interested in testing frictional performance in situ on equipment, especially related to material handling conveyors.
 
Ability to develop a test device for assessment of chain lubricants.

Thermal characterization.

Prescreening fluid formulations for bigger approval tests or field trials.

Absence of ASTM standards and methods for lubricant friction (both oil and grease) creates challenges in generating Stribeck plots. Lack of precision statement and reference fluids creates challenges in benchmarking and comparing inter-lab data.

There is an increasing need to consider different contact materials, the most common being metal to plastics and ceramics or elastomers from sealing systems. Additives response is not same as metal/metal contact pairs as well as material compatibility.

There was no surprise instance as the specifications demand the right choice or tribology. If we go beyond tribology or the right test, we may be a victim.

In some cases there are missing ASTM, CEN or DIN standards. These industrial standards and their results would help to communicate with suppliers and customers.

In your experience, have new industrial applications (e.g., EVs, renewable energy systems) increased the demand for novel lubricant formulations?
Yes 84%
No 16%
Based on an informal poll sent to 15,000 TLT readers.
Understanding the difference between mineral and synthetic esters in relation to viscosity pressure coefficients.

Try to put together a more in-depth analysis. Rotating bomb oxidation test (RBOt) and varnish potential.

EV lubricants’ and automatic transmission oils’ viscosity are getting lower and lower. With high RPM, such as 20,000, foam and air entrainment will be the problems. Then we add the defoamers. The defoamers settle down at the bottom of the tank before the required shelf life. Then foam problem occurs and ends up operation should be stopped.

Not having the right test method is a problem; we need to develop non-traditional tests.

There is no real test which fulfills the complete spectrum of load. Thus there are multiple tests available, and customers love their own tests. For oil, greases and things like this, you have the choice between variable tests. In special fields like, e.g., cold forging, there is only limited availability, so you always have to develop your own test.

Repeatability of test results and translation from lab to industrial applications.
 
The challenge is always to break down requirements on system test level down to the tribocontact and derive the right contact operating conditions.

Robot greases for synchronizers and reducers have complex motions, and the contact conditions of loads, speed, temperatures and precise geometry are difficult to replicate. This makes the development of new greases difficult as there are no suitable screening methods. It is similar to how it was with constant velocity joint greases 40 years ago.

New additives for better surface wettability and less staining property.

Changing the viscosity may trigger a different friction and wear behavior; mixed lubrication will start to appear earlier and in a different spot/location in a machine.

The stress patterns associated with modern applications such as electric drives are not yet fully understood. There is a lack of recognized, practical test methods, for example, for assessing the high-speed suitability of lubricating greases.

There is a huge lack of profound testing methods and/or test rig setups for future challenges like “one-fluid topic” or “gear performance oils.”

Q.2. What innovative testing methods or instrumentation advancements have significantly improved your ability to evaluate lubricant performance?

The use of statistical tools.

The most impactful improvement has been the integration of multi-scale testing approaches combining tribometer-level screening with gear-level validation. In particular, high-resolution 3D surface characterization (ISO 25178-based) has enabled better tracking of surface evolution and lubricant retention mechanisms. Time-resolved temperature and torque monitoring in custom gear test rigs has improved the understanding of friction under realistic loading conditions. Laser-textured surface testing under controlled lubrication regimes has provided insights into lubricant transport and film stability. Coupling experimental data with thermal elastohydrodynamic lubrication (TEHL)-based modeling has significantly enhanced predictive capability, especially for film thickness and friction behavior. These combined approaches allow more reliable evaluation compared to conventional standalone tests.

Thermogravimetric analysis (TGA), viscometry and tap/thread/cut tribology, four-ball wear analysis.

Extreme pressure and antiwear criteria and tests are so important with new modes of transportation such as EV and electric turbines. Long term, in the field, testing is required beyond the bench.

The E-Lub Tester. This electrified tribometer allows us to evaluate lubricating conditions of oils and grease under varying speed, load and lubricant temperatures by means of impedance measurement. It also offers a breakdown test option with a signal generator that can mimic drivetrain shaft voltages to investigate the dielectric strength of a lubricated roller bearing under real-life conditions.

Internally developed methods.

Particle image velocimetry (PIV) analysis.

Reciprocating tribometers, rolling contact fatigue machines or two roller apparatus testing with same materials, temperature and conditions simulating the actual condition as much as possible.

A proprietary method to quickly assess the chain length distribution of hydrocarbon-based materials to understand the impact of competing mechanisms of shear and oxidation.

More tests around conductivity and impact of electric fields on fluids.

Four-ball test.

One key advancement is the development of highly configurable tribometers that can simulate complex and application-specific conditions. Modern systems allow precise control of load, speed, temperature and environment, enabling testing under extreme conditions and more realistic operating scenarios. This flexibility is critical for emerging applications where standard test methods are insufficient. Another important improvement is the integration of in situ measurement techniques, such as real-time friction monitoring, electrical contact resistance (ECR) for film formation analysis and acoustic emission for wear detection. These tools provide continuous insight into lubrication regimes and surface interactions, rather than relying solely on post-test analysis. Advancements in surface characterization and imaging, including 3D profilometry and high-resolution microscopy, have also enhanced the ability to quantify wear, surface damage and tribofilm formation with high precision.

Integrating a synchronized, multi-sensor data acquisition (DAQ) system enabling real-time correlation between friction, contact potential, temperature and load to resolve transient lubrication regimes.
 
Which of the following areas do you believe has benefited the most from advancements in lubricant testing instrumentation?
Oxidation stability                 32%
Tribological performance (wear/friction) 76%
Contaminant detection                   24%
Viscosity control                  20%
Other                 10%
Based on an informal poll sent to 15,000 TLT readers. Total exceeds 100% because respondents were allowed to choose more than one answer.
Modifications in terms of test conditions of pre-existing standardized test methods. Multifunctional test equipment. Design of new test methodologies based on well-known and proven tribometry.

The twist compression test (TCT) was developed to address many of these challenges. The upper annular specimen can be massed produced and plated or polished to match the production tooling. In one research project we were able to cut identical annular specimens from HDPE, nylon, bronze and D2 tool steel. The contact geometry in the TCT is sliding flat-on-flat contact so the counter-surface must be flat. Using the TCT for testing lubricants for a roller (rolling line contact) or ball bearing (rolling point contact) would not produce valid data. The TCT is designed to cause the lubricant to fail in every test. A lot can be learned by interrupting the test and examining the test specimen surfaces including surface analysis techniques to show the changes in tribofilms as the lubricant is being depleted.

I’ve been working on instrumenting conveyor systems to monitor drive torque and power consumption in real time.

Accurate inline measurement of wear, combined with ageing characteristics.

Infrared spectroscopy analysis on different wavelengths.

Pressure differential scanning calorimetry (PDSC) was extensively used to screen a wide range of raw materials for this project.

SRV tribometer.

For EV fluids, the ability to apply controlled potential and current has been helpful. While instrument advances are great, usability of such innovations within the lab by operators is equally important. Simplicity and ease of operation matters.

Transforming tribometers to test other than steel contacts and different contact geometry. Also testing conditions have to be adjusted (oscillation, speed, contact pressures, temperature, etc.). Modifying tribometers like SRV or reciprocating rigs is a challenge for R&D, and even more for standardization.

Tribotesting for EHL.

Research on the dielectric compatibility of lubricants simultaneously with their rheological properties.

Membrane patch colorimetry (MPC) has become a key predicter in oil life.

The instrument of lubricity testing has been advanced in a couple testing machines and instruments since EVs started in the markets.

More than a particular test method, statistical analysis has helped me.

Development of new adaptors, i.e., radially loaded bearing adaptors in rotary tribometers allowing bulk testing of lubricant batches.

Your in-house differential bolt wear and shim friction tester to better reflect differential performance and lifetime in reference to tribological parameters.

Friction and wear testing equipment has become a lot more sophisticated in the last 30 years. The SRV test equipment is a lot more versatile and can be used to simulate lots of contact conditions. The four-ball wear and extreme pressure (EP) tests are still widely used despite them not being very applicable to grease lubricated contacts. The grease industry needs to move on beyond four-ball testing.

Adapted tribotesting—modifying and adapting a test rig to meet a specific challenge. Also, oxidation stability testing and evaluation, including remaining antioxidant levels.

Modern test benches are equipped with an increasing number of sensors and generate high-frequency measurement data (e.g., impedance measurement or vibration measurement). The meaningful interpretation of this data provides an “insight” into the tribosystem (Tribometry 4.0).

In-house solutions, because of lacking (new) standards.

Editor’s Note: Sounding Board is based on an informal poll sent to 15,000 TLT readers. Views expressed are those of the respondents and do not reflect the opinions of the Society of Tribologists and Lubrication Engineers. STLE does not vouch for the technical accuracy of opinions expressed in Sounding Board, nor does inclusion of a comment represent an endorsement of the technology by STLE.