A comparison of the heating value among diesel, neat palm oil,the palm oil–diesel–ethanol blend, ethanol, and microemulsions isprovided in Fig. 5. The results show that the microemulsion-basedbiofuels had slightly lower heating values (38.6–39.5 MJ/kg) thanneat diesel (45.1 MJ/kg). This is attributed to the fact that our bio-fuels contained more oxygen in the system (e.g., ethanol blends of20 vol.%), which reduced their heating values, as expected. None-theless, the heating value of the microemulsion biofuels containingethanol were 12% lower than those of neat diesel and 0.5% lowerthan that of palm oil in some formulas, which is not an overwhelm-ing difference. Moreover, these results are consistent with those ofDo et al. [14]; they provided flame imaging of microemulsion fuels,which indicated the region of the gas phase combustion of the fuelswith higher degrees of oxidation due to the presence of oxygen inthe fuel.