## 2 Experimental Methodology  
### Fuel Tested Physicochemical Properties and Sample Characterization  
Considering the use of fuel for a diesel engine, it is advantageous for the fuel's properties to be as close as possible to those of diesel fuel. To this end, an attempt was made to change the physical properties of canola oil by adding n-hexane. Adding n-hexane to canola oil in a relatively small amount had a beneficial effect on the physical and chemical parameters of the canola oil-based blend. The chemical compound n-hexane has specific properties, i.e., surface tension, density and viscosity, which are much lower than those of diesel fuel. The tests were carried out for blends of canola oil and n-hexane, the basic physicochemical parameters of which are summarized in Table 1. The determinations of the prepared blends are shown in Table 2. The values of selected physicochemical properties of canola oil-n-hexane blends are shown in Figures 1-3 [18]. Density measurements were made in accordance with the procedure contained in PN-EN ISO 12185 [22]. An accurate density meter of type DMA 4500 was used. The results were presented as the mean value of two measurements. Uncertainty for density measurement \(\pm\)0.00005 g/cm\({}^{3}\) was determined by the supplier of the test device and was confirmed by a calibration certificate of the measuring device. The accuracy of the temperature given by the manufacturer was equal to \(\pm\)0.001 K. Commercially available refined canola oil was blended with n-butanol in volume fractions of 5 to 20%. The main components of canola oil are unsaturated fatty acids, such as oleic, linoleic and linoleic acids. Their content in canola oil exceeds 90%. On the other hand, n-hexane (C\({}_{6}\)H\({}_{14}\)) is an organic chemical compound from the alkane group. Hexane isomers are highly unreactive and are often used as solvents in organic reactions because they are highly non-polar. They are also included in gasoline. N-hexane is produced during petroleum refining. The industrial product is a fraction boiling at 65-70 \({}^{\circ}\)C. For comparison, tests were also conducted for typical diesel fuel (DF). The physicochemical properties and test methods of the diesel used in the study were in accordance with the Polish standardPN-EN 590 [23]. The surface tension of the canola oil and n-hexane blends was measured by the Kruss K9 tensiometer according to the platinum ring detachment method at 293 K. In all cases, 10 measurements were performed. The standard deviation was 0.1 mN/m. The viscosity measurements of the canola oil and n-hexane blends were performed with the [PERSON] viscometer, AMvn, with a precision of 0.0001 mPas and an uncertainty of 0.3% [18]. The addition of n-hexane to canola oil reduced the density of the fuel, the values of which approach that of diesel fuel (Figure 1). For the addition of 20% vol. n-hexane, the density value of the blend with canola oil was lower than that of pure canola oil by approx. 4%. A similar effect of the addition of n-hexane to canola oil applied to kinematic viscosity (Figure 2) and surface tension (Figure 3). The addition of 20% n-hexane reduced kinematic viscosity by about 23 mm\({}^{2}\)/s and surface tension by about 6.5 mN/m (this is a lower surface tension value than for the diesel fuel under test). of blends of canola oil with n-hexane, including the values of the derived cetane number DCN and the parameters of the combustion process (ID, CD, MPR). The tests were carried out according to the method in accordance with ASTM-D7668 standard [21]). The key purpose of this instrument is to determine the DCN according to standard testing procedures [21,28]. The same instrument was used by [PERSON] et al. [29] and [PERSON] et al. [30]. The calibration parameters, as summarized in Table 3, were maintained throughout the test cycle. According to standard ASTM-D7668, the combustion chamber of the device is mounted with an injector of Bosch Serial No. 0445110181. The injector has a 6-hole atomizer with holes of 0.17 mm diameter.