Friction and wear reduction in internal combustion engines are crucial for improving efficiency and durability. This study investigates the effect of microtextured surfaces on friction power loss in an engine’s piston ring-cylinder system. A numerical analysis was conducted on piston rings equipped with dimple-shaped microtextures using AVL Excite Piston & Rings, modelling a hard chromium-coated piston ring and a cast iron cylinder. The goal was to determine the optimal surface texture parameters that minimize friction power loss under typical urban driving conditions with SAE 0W-30 oil. A two-step Design of Experiments (DoE) approach was employed, where the first step involved mapping the effects of texture parameters, i.e., dimple depth (A = 0.5, 1, 1.5 µm), dimple distance (B = 120, 160, 240 µm), and dimple diameter (C = 50, 60, 70 µm), to identify influential factors. The second step aimed at locating a parameter configuration with minimal friction power loss. The results demonstrated that the optimized texture parameters can significantly reduce friction power loss. The lowest friction power loss of 8.96 W was achieved with a dimple depth of 2 µm, distance of 80 µm, and diameter of 60 µm, which contributed to an 8.3% improvement over the reference surface. The model built to describe the investigated texturing approach exhibited a strong correlation with an R² value of 0.93, and the deviation between predicted and measured values was below 1%. Future work will involve tribometer tests to experimentally validate the optimized parameters and confirm the simulation results.

This study aimed to develop an experimental method for producing artificially aged oil with properties—such as coefficient of friction, average wear scar diameter, and antiwear additive content—similar to those of used oil contaminated with alternative fuel, sampled after 129 h of engine test bench operation. A design of experiment (DoE) methodology was applied to examine the effects of various parameters and identify optimal settings. Friction and wear tests were conducted using an Optimol SRV5 tribometer in a ball-on-disc configuration, while wear scars were analyzed with a Keyence VHX-1000 digital microscope. Oil analysis was conducted with an Anton Paar 3001 viscometer and a Bruker Invenio-S Fourier-transform infrared spectrometer. The DoE results showed that the heating duration had a negligible effect on oil degradation. Aging time primarily affected changes in the friction coefficient and average wear scar diameter, whereas aging temperature was the primary factor influencing the anti-wear additive content. Gaussian elimination identified the optimal aging parameters as 132.8 °C and 103.1 h. These results were confirmed through surface analysis using a ThermoFisher NexsaG2 X-ray photoelectron spectrometer, which showed that the tribofilm composition of the used oil most closely matched that of artificially aged oils prepared at 120 °C for 96 h and 140 °C for 120 h. The strong correlation between the predicted and experimentally confirmed conditions demonstrates the reliability of the proposed method for replicating realistic aging effects in lubricating oils.

The aim of this paper is to develop an experiment design to determine the wear and friction parameters of an SAE 0W20-grade reference oil and an SAE 0W20-grade used oil contaminated with E20 fuel. Wear tests in a ball–disc arrangement were conducted at temperatures and loads established using Design of Experiments. A surface analysis of the wear scars was performed using a digital microscope, while the oils were investigated using a viscometer and a Fourier-transform infrared spectrometer. Design of Experiments was further employed to develop two models using R software. For the reference oil, the developed model was only suitable for screening, while the model for the E20 fuel contaminated used oil showed a 9.8% difference between the measured and estimated coefficients of friction.

During tribometer experiments, the condition of the applied lubricants plays a crucial role in determining friction and wear properties. Oil degradation can significantly influence measurement outcomes, making it essential to understand the chemical changes that may occur during tribometric experiments. The objective of this study is to systematically investigate the source of silicone contamination and its temperature dependence. Tribometer experiments were conducted at 40, 60, 80, 100, and 120 °C, followed by FT-IR spectroscopy to analyze the lubricant after each measurement. Additionally, wear scars were examined using X-ray photoelectron spectroscopy to determine the presence of silicone within the surface layers. To assess potential alternative contamination sources, a single-drop system was employed, which excludes tubing, thereby providing a controlled environment to verify the origin of the silicone peaks. The results of this study are expected to enhance the reliability of tribometer measurements by identifying contamination sources and optimizing the experimental setup.