The article presents the results of combined tribological and physicochemical studies of engine oils used in Autosan Sancity M12LF city buses at various mileages exceeding the manufacturer’s recommended oil change interval (60,000 km). Semi-synthetic oil of ACEA E4, E7, SAE 10W-40 class was analyzed, with samples taken from five buses with different degrees of interval exceedance (− 19% to + 35%). To address outlier influence, both classical Pearson and a more robust Spearman’s rank correlations were applied. While Pearson correlation suggested a very strong relationship (r = − 0.9946) between sulfur content and wear scar diameter, Spearman’s robust method confirmed a strong but more reliable association (r = − 0.810), indicating that classical correlation was inflated by outliers. A potential relationship was demonstrated between the degree of oil change interval exceedance and degradation of phosphate anti-wear additives. Anti-wear additive degradation follows a non-linear pattern and accelerates with successive exceedances of the recommended change interval. A degradation thresholds were identified: oil degradation becomes more pronounced after exceeding the interval by 10,000–15,000 km, while exceeding by more than 15,000–20,000 km results in potentialy increased engine component wear and elevated failure risk. The content of abrasive metals (Fe, Cu) in used oils significantly increased compared to fresh oil, with particularly high iron concentration (131.67 ppm) observed in the sample with the greatest interval exceedance. After exceeding the interval by 20,000 km, phosphate anti-wear additive depletion was 73% higher than when exceeding by 5000 km. The research results provide important information for bus fleet operators, allowing more precise determination of engine oil change intervals, which translates into extended engine life and reduced operating costs.

This article shows the effect of the addition of effective microorganisms and silver on the exhaust gas composition and fuel consumption. Exhaust emission standards are becoming increasingly stringent, which makes it difficult for engine manufacturers to meet them. For this reason, intensive work is underway to use alternative propulsion systems on ships, and for diesel engines, alternative fuels. Among other things, this applies to mixtures of petroleum-based fuels with vegetable oils and their esters. Unfortunately, their use, due to their physicochemical properties, can negatively affect the performance of the engine and the wear of its components. Therefore, the aim of this study was to see how additives of effective microorganisms in the form of ceramic liquid and tubes, and a silver solution and colloidal silver would affect some engine parameters, including the exhaust gas composition and fuel consumption. The authors are not aware of the results of previous research on this issue. The tests were carried out on a diesel engine for four types of green additives at concentrations of 2% and 5%, at different ranges of its load. The additives added to the diesel fuel were characterised, and the test stand was presented, along with the parameters of the tested fuel. The effect of additives on selected engine parameters, including fuel consumption, was presented. The characteristics of hourly fuel consumption and selected components of the exhaust gas, including nitrogen oxides, carbon monoxide and carbon dioxide as a function of the concentration of ecological additives are shown and analysed. It was found that the most beneficial additive that had a positive effect on the exhaust gas composition and fuel consumption was a silver solution in a 2% concentration. There was a decrease of up to 4% in the NO_x content of the exhaust gas, a decrease in carbon monoxide of more than 28%, a decrease in carbon dioxide of 4.6% and a decrease in fuel consumption of around 3% was achieved under the tested conditions. The use of these additives is an innovative solution that has a positive impact on reducing the emissions of harmful compounds into the atmosphere. In further research, it will be necessary to study the effect of this additive on the combustion process in the engine and the wear of its components, as well as to confirm the results obtained in real operating conditions.

In the article, acid number as a parameter characterizing engine oil were characterized. The next part of the article discusses the phenomenon of aging and degradation of engine oil. The factors that influence on this phenomenon have also been analyzed. In the further part of the article, the methodology of testing the used oil samples with the addition of effective microorganisms and silver solution was described. In the main part of the article the measuring test stand and acid number value for fresh and used oil compared to oils with the addition of microorganisms and a solution of silver and colloidal silver was shown. Next the analysis of the influence of these additives on the acid number value was made. The article was completed conclusions.

The article presents new propulsion concepts and related new energy sources of modern means of transportation. One of them is hydrogen fuel cells, widely regarded as one of the most promising and alternative solutions due mainly to their ecological nature. Also presented, the biggest problem...

This paper presents the effect of environmentally friendly additives on selected parameters and microbial degradation of Marine Diesel Oil (MDO). Microbiological contamination is a serious problem in MDO and other petroleum products. For this reason, it was decided to investigate the effects of environmentally friendly additives such as silver solution and colloidal nanosilver, as well as effective liquid microorganisms and ceramic tubes with different percentages of them in diesel oil (MDO) on its selected parameters and inhibition of bacterial and fungal growth. The tests were conducted on a mixture of fuel with four types of environmentally friendly additives at concentrations of 2% and 5%, and on fuel without any additives. The effect of the additives on selected diesel parameters, including flash point, water content and acid number, as well as density and kinematic viscosity, is presented. The diesel oil was also subjected to microbiological tests. It was found that the most beneficial additive that positively influenced diesel parameters and microbial degradation was a silver solution at a concentration of 2%. The lowest ignition temperature was obtained when ionic silver was used, i.e. 60 °C, which is closest to the value for pure diesel fuel. The addition of effective microorganisms in liquid form to the fuel in an amount of 2%, increases the ignition temperature to 62.2 °C and this is the highest value obtained in comparison with other additives. The lowest water content in the test samples was obtained for the effective microorganisms in ceramic form at − 0.0068%, while the highest value was obtained for the silver solution at 0.0123%. At 100 °C, the highest kinematic viscosity was obtained for EM in ceramic, at 1.11 mm²/s. While for pure oil it was 1.03 mm²/s. For pure diesel, a value of 1.1 × 106 cfu/1 dm³ for bacteria and 7.3 × 103 cfu/1 dm³ was obtained. For each type of mixture, a value of less than 1 × 102 cfu/1 dm³ for bacteria was obtained, while in terms of fungal counts in the mixtures, a decrease of 73 times is also observed for diesel mixed with effective microorganisms in liquid form and ceramics, 48 times less was recorded after the use of non-ionic silver. The use of these additives is an innovative solution that has a positive effect on slowing down microbial degradation, without any loss of diesel performance.

In the article, changes in the properties of oils during operation were characterized. The main reason for this is the continuous aging process of the used oil caused by the interaction of oxygen contained in the air, which reacts relatively easily with hydrocarbons and the oxidation process is accelerated just by high temperature. Then the problem of microorganisms occurring in petroleum products and their effect on the properties of oils and the operation of the internal combustion engine was presented. The next part of the article presents effective microorganisms, i.e. what they are and how they work, in particular, their composition and appropriate development conditions. In addition, some of their specific applications were briefly described. In the next part of the article, the research methodology, applied oil samples with additives of effective microorganisms, both for fresh oil and used oil were described. In addition, the measuring test stand with instrumentation and measuring device was shown. The main part of the article contains the characteristics of dynamic viscosity as a function of temperature for fresh oil and used oil compared with oils with the addition of microorganisms in liquid form and ceramic tubes. The developed graphs enabled analysis of the effect of the addition of microorganisms on oil viscosity as ecological products.