Fig. 1. Schematic diagram of the test process

Fig. 2. Infrared spectra of Mobil Jet oil Ⅱ lubricating oil, fuel oil and lubricating oil mixed with 50% fuel oil

Fig. 3. (a) Infrared spectra of lubricating oil samples mixed with different fuel contents; (b) characteristic region area of the sample with 0% fuel content; (c) characteristic region area of the sample with 2% fuel content; (d) characteristic region area of the sample with 3% fuel content; (e) characteristic region area of the sample with 5% fuel content; (f) characteristic region area of the sample with 10% fuel content; (g)characteristic region area of the sample with 25% fuel content

Fig. 4. Working curve fitting using Spectrum Quant software

Table 1. Infrared spectrometer parameters

Table 2. Forecast results of working curve

Table 3. Repeated determination results

Table 4. Blank fuel peak area

Table 5. Fuel quantitative results of the two detection methods