The correlation between newly approved EN 15751 and the internal diesel injector deposits (IDID) due to fuel oxidative deterioration has not been made clear. In the present research, the Rancimat method was slightly modified to research the relationship between fuel oxidative deterioration and the deterioration products generated from the fuel. After heating fuel at 120 to 150°C for a set period, insoluble deterioration products (IDID-like substances) were generated and their weights were measured. At the same time, the shifts of the conductivity in trap water were analyzed from a new perspective, and its relationship with the deterioration products was investigated.
At 120°C and 130°C, conductivity rising rates after the inflection point (this set of data represents the rate of organic acid generation in the fuel, and we named “Oxidation rate”) exhibited a strong correlation with the quantity of deterioration products. In contrast, the correlation between the oxidation rate and the quantity of deterioration products was lower at 140°C and 150°C than at 120°C.
A relationship between the oxidation rate of FAME-blended fuels and the number of double bonds in the FAME content was observed. In particular, the results of analyzing the content of the deteriorated fuel suggested polyunsaturated FAME as a factor in the significant acceleration of the oxidation rate.
The results of this research demonstrate the possibility of simultaneously measuring oxidation stability due to the inflection point and deposit productivity due to the oxidation rate with the Rancimat method.