## 1 Introduction  
The problem of climate warming requires reducing greenhouse gas emissions in all branches of the human economy. This is particularly important in the transportation and power generation sectors [1, 2]. This is leading to the replacement of fossil fuels with renewable fuels [3]. These fuels include vegetable oils and their esters [4, 5, 6]. Research on the use of vegetable oils as engine fuels is being conducted by many scientists [7, 8, 9]. However, the results of studies when the engine is fueled with pure vegetable oil tend to be unfavorable compared to the results obtained when fueled with diesel [10, 11, 12, 13, 14]. The main problems associated with the use of vegetable oils in diesel engines are low thermal efficiency due to high viscosity and carbon residues, and high smoke levels. Many publications deal with fuels that are blends of vegetable oils and other components [15, 16, 17]. Potential additives to improve blend properties over pure canola oil include n-hexane [18]. An example of a paper confirming the beneficial properties of n-hexane and fuel blends with waste plastic fuel and jatropha biodiesel and diesel fuel is [19]. The results presented there confirm that the addition of n-hexane can improve the physicochemical properties of the fuel and enable the reduction in CO and NOx in the engine exhaust. Additionally, engine research reveals that the fuel samples with n-hexane added have improved thermal and volumetric efficiencies and lower BSFC (brake specific fuel consumption) [19].  
Among other things, the addition of n-hexane results in improved low-temperature properties, as well as improved auto-ignition and combustion properties. Note that it is particularly important to test fuels and their blends on diesel engines, which are equipped with common rail injection systems that allow the fuel dose to be divided into several parts.  
Testing of self-ignition and combustion properties can be carried out using various methods. These methods include engine methods and methods implemented in a constant volume chamber. Depending on the method adopted and the test conditions, the results may vary. In particular, it should be borne in mind that tests in a constant volume chamber are carried out under established conditions that may differ from those in the engine tests [20].  
Tests of blends of canola oil and n-hexane carried out in a constant volume chamber under conditions corresponding to diesel fuel tests in accordance with ASTM-D7668 [21] showed little effect of the addition of n-hexane on the value of the derived cetane number and the parameters of the combustion process. On the other hand, tests conducted under dynamic conditions on a passenger car with a diesel engine showed a significant effect of the n-hexane additive on the combustion process and the performance parameters that depend on it.  
The novelty of the article, in addition to proposing the use of n-hexane as an additive to canola oil, is the study of the self-ignition properties of the blends in question under constant volume chamber combustion conditions. Due to the invariability of the fuel injection conditions, this ensures very high repeatability of the results in terms of both DCN and ignition delay.