This paper describes a particular procedure, based on ASTM D7214 and ASTM E 2412, which has been defined to improve oil oxidation quantification in used engine oils. Taking into account typical problems that can be found in this type of samples, thermal oxidation and fuel dilution, response on FT-IR spectra has been analyzed considering also the effect of oil formulation. Two special zones have been considered inside the typical wave number range for oxidation quantification, where those problems can be detected and assessed more easily. Zone A between 1,725 cm , where esters as main products for detection of fuel dilution problems when diesel engine is operating with biodiesel.

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A study of the injection process and spray behavior has been made for three different fuels. In particular, blends of rapeseed methyl ester (RME) with standard diesel fuel at 5% and 30% of biodiesel have been used for the current study, as well as pure RME.Hydraulic characterization of an 8-hole nozzle has been carried out using these three fuels, in order to explore and analyze the influence of fuel properties on mass flow rate and momentum flux at the nozzle exit. Additionally, spray visualization tests have been made in order to get information about spray cone angle, which allows the characterization of air-fuel mixing process. Finally, a theoretical derivation has been used to obtain further details of the microscopic characteristics of the spray and compare air-fuel mixing efficiency for the different biodiesel blends.