Fuel Properties | Gasoline | Bioethanol |
Molecular weight [kg/kmol] | 111 | 46 |
Density [kg/l] at 15⁰C | 0.75 | 0.80-0.82 |
Oxygen content [wt-%] | 34.8 | |
Lower Calorific Value [MJ/kg] at 15ºC | 41.3 | 26.4 |
Lower Calorific Value [MJ/l] at 15ºC | 31 | 21.2 |
Octane number (RON) | 97 | 109 |
Octane number (MON) | 86 | 92 |
Cetane number | 8 | 11 |
Stoichiometric air/fuel ratio [kg air/kg fuel] | 14.7 | 9.0 |
Boiling temperature [ºC] | 30-190 | 78 |
Reid Vapour Pressure [kPa] at 15ºC | 75 | 16.5 |
Comparison of Gasoline and Bioethanol
Energy content
Bioethanol has much lower energy content than gasoline (about two-third of the energy content of gasoline on a volume base)
Octane number
Octane number of ethanol is higher than that for petrol; hence ethanol has better antiknock characteristics. This increases the fuel efficiency of the engine. The oxygen content of ethanol also leads to a higher efficiency, which results in a cleaner combustion process at relatively low temperatures.
Reid vapour pressure (measure for the volatility of a fuel)
Very low for ethanol indicates a slow evaporation, which has the advantage that the concentration of evaporative emissions in the air remains relatively low. This reduces the risk of explosions. However, the low vapour pressure of ethanol, together with its single boiling point, is disadvantageous with regard to engine start at low ambient temperatures. Without aids, engines using ethanol cannot be started at temperatures below 20ºC. Cold start difficulties are the most important problem with regard to the application of alcohols as automotive fuels.
