The paper focuses on the assessment of selected physicochemical properties of microemulsion containing 5% by mass (m/m) of surface active compounds (SAC), i.e. Span20 and Crilet4 as well as 10 % (m/m) of distilled water dispersed in diesel fuel (DF). In particular temperature dependent properties such as: flash point (FP) and cold filter plugging point (CFPP) as well as lubricity, friction coefficient, corrosiveness and kinematic viscosity of tested fuels were examined. It was found that the tested surfactants and water added to DF increase microemulsion FP by 13 ºC. For this reason, it can be stated that tested microemulsion is safer than typical DF. On the other hand it was found that the CFPP of the tested microemulsion is also adequately higher. It means less usefulness of such fuel during winter periods. Based on the research results it can be stated that addition of tested surfactants slightly worsens the lubricity of DF. However, the same surfactants in the presence of dispersed water reduce the friction in the tribological node and improve the lubricity of the tested microemulsion. Research showed that tested microemulsion system is not corrosive as well as its kinematic viscosity meet requirements of EN590 standard. Based on all these findings, microemulsion is considered as safe and such fuel can be recommended for engine tests without the risk of its damage.

The article presents the concept of modern engine oils reliability assessment. The strategy taken in practice for changing the engine oil based on a predetermined working time may lead to the replacement of engine oil being still in operational condition caused by the selected status parameter. Such conclusions are coming from the conducted tests of mineral oils. It is reasonable to carry out reliability of engine oils assessment in operation, for synthetic oils dominating on the automotive market.

W artykule przedstawiono wyniki badań zadymienia spalin silnika o zapłonie samoczynnym AD3.152 zasilanego olejem rzepakowym (OR)oraz jego mieszaninami z eterem dietylowym (DEE). Wszystkie niezbędne badania wykonano w warunkach ustalonych dla wybranych prędkości obrotowych wału korbowego tj. 1000, 1500 i 2000 obr/min oraz obciążeń 40, 80 i 120 Nm. Uzyskane wyniki potwierdzają, że dodatek eteru dietylowego w objętości 40% do oleju rzepakowego zmniejsza zadymienie spalin nawet o ok. 50% w stosunku do silnika zasilanego olejem rzepakowym.

The paper presents research results of selected fuel microemulsions. In particular the corrosion properties of these microemulsions were investigated. Necessary research was carried out in line with requirements of ASTM D130 standard for fuel microemulsions containing 4 and 8 % by volume of distillated water dispersed in diesel oil. On the base of research results, it can be stated that both tested fuel microemulsions had unfavourable corrosion properties when compared to diesel oil and distillated water