Engine oil condition and tribological performance are strongly interrelated. Accordingly, oil condition monitoring is common in various applications. This is especially important, as oil condition depends on the fueling and utilization profile of an internal combustion engine. Common practice involves the measurement of various parameters, such as the total acid number and total base number, oxidation, nitration, viscosity, and elemental composition; thus, it can be time-consuming and resource-intensive. This study provides a methodology for rapid analysis for large vehicle fleets or sample sizes, using only Fourier-transformed infrared spectroscopy and the subsequent multivariate data analysis offers a rapid alternative to commonly available methods. The described method provides a rapid, cost-efficient, and intuitive approach to uncovering differences in the oil condition. Furthermore, understanding the underlying reasons in engine construction and the resulting chemical degradation is also possible.

This study highlights how the results from an artificial engine oil aging method compare to used engine oil samples collected from a vehicle fleet. Additionally, this paper presents the effect of contaminating the oil during aging with synthetic fuel alternatives on the physical and chemical properties of artificially aged engine oil samples. A laboratory-scale artificial thermo-oxidative aging experiment was conducted on multiple samples of commercially available formulated fully-synthetic SAE 0W-30 engine oil. The goal of the experiment was to establish the validity of the artificially aged samples as well as the validity of the underlying process in reproducibly fabricating small batches of aged engine oil with comparable chemical and physical properties to real-life used oils. Eight samples were subjected to distinct load cases (temperature, air flow rate, sample volume and aging time). Six additional samples were subjected to an intermediate load case, with five of them contaminated with selected conventional fuels and novel automotive fuel candidates. Conventional oil analysis was conducted on each sample to determine oxidation, residual additive content, kinematic viscosity and total base number. Additionally, analysis results were compared to in-use engine oil samples through PCA. The resulting oil condition after aging is in accordance with independently published results in terms of zinc dialkyldithiophosphate content and kinematic viscosity. Contaminated aging with OME _3-5 resulted in a drop in antioxidant content and elevated kinematic viscosity. Based on the comparison with in-use samples, artificial aging of 200 mL engine oil at 180 °C with 1 L/min air flow for 96 h can produce similar oil conditions as mixed vehicle use for 7000 km.

Non-fossil fuels for the commercial and passenger vehicle sector are gaining more importance due to their positive effects on exhaust gas emissions. Ongoing research investigating a broad variety of biofuels, synthetic fuels and regenerative fuels shows that a reduction of CO₂ emissions can be possible without major modifications to the existing vehicle infrastructure. An internal combustion engine is a complex system of physical and chemical mechanisms, all of which contribute to the performance output, exhaust gas composition, durability and longevity of the engine. Modifying the fuel will not only result in differing chemical reactions and thermodynamic efficiency but will also affect friction and wear through the dilution and degradation of the lubricant. This study aims to investigate the variation of friction and wear in a model system due to the introduction of oxymethylene ether and regular diesel fuel to the lubricant. High-frequency reciprocating rig experiments will be carried out on 100Cr6 steel specimen with laboratory aged fully formulated commercially available SAE 0W-20 grade engine oil containing defined amounts of OME_3–5 and regular diesel fuel. The surface of the steel specimen will be analysed using optical microscopy and scanning electron microscopy.

Engine oil degradation and tribological properties are strongly interrelated. Hence, understanding the chemical processes resulting in additive depletion and degradation products is necessary. In this study, in-service engine oils from petrol and diesel vehicles were analyzed with conventional and advanced methods (mass spectrometry). Additionally, the effect of the utilization profile (short- vs. long-range) was studied. Petrol engine oils generally showed accelerated antioxidant and antiwear degradation and higher oxidation, especially in the case of a short-range utilization profile, which can be attributed to the higher air-to-fuel ratio (more rich combustion) compared to diesel engines. A detailed overview of oxidation and nitration products, as well as degradation products resulting from zinc dialkyl dithiophosphate and boron ester antiwear additives, diphenylamine antioxidants and salicylate detergents is given. A side reaction between oxidation products (aromatic carboxylic acids) and the boron ester antiwear is highlighted. This reaction was only detected in the petrol engine oils, where the oxidation products were measured in a high abundance. However, no side reaction was found in the samples from the diesel vehicles, since there the aromatic carboxylic acids were largely absent due to lower oxidation.