“…Based on previous research, it is known that the quantum chemical reaction of fuel in an internal combustion engine is complex [ 40 ], as it includes molecular modeling to determine the complexity of the combustion reaction of each active group, such as the hydroxyl group, the ethyl group, and the isooctane group [ 41 ]. On the other hand, from the bond properties data for ethanol (see Table 2 ) and isooctane (see Table 5 ), of the 9 bonds owned by ethanol, 8 bonds are non-rotatable, while isooctane has 23 non-rotatable bonds out of 25 bonds.…”