The common types of available fuel-mixes are listed in Table 5.
The energy content and RON (Research Octane Number), of
ethanol, other fuels and mixes are also summarized in Table 5. The
octane rating of petrol is measured in a test engine and defined by
comparing the mixture of iso-octane and heptane that would have
the same anti-knocking capacity as the tested fuel itself. Fuel with
the same knocking characteristics as a mixture of 95% iso-octane
and 5% heptane would have an octane rating of 95. Of course, the
tested fuel does not contain just iso-octane and heptane in the
given proportions, but will have the same detonation resistance
characteristics. Since some fuels perform better than pure isooctane,
octane numbers in excess of 100 are now accepted in a
modified definition. The most common rating is the RON (Research
Octane Number), determined in a test engine with a variable
compression ratio under controlled conditions (600 rpm). The
Motor Octane Number (MON) is also used, and often considered a
better measure of fuel behavior under load, as determined in a
900 rpm test engine. MON will normally be about 8e10 points
below RON. The low density of gasoline and ethanol are reflected in
the higher mass than volume heat content of the fuel.
Ethanol has appropriate properties for spark ignition IC engines.
Its MON and RON are respectively 90 and 109, on average 99
compared to 91 for regular gasoline. The lower heating value (LHV)
of ethanol is two-thirds that of gasoline. Bio-ethanol fuel is used in
IC engines as 5e26 percent anhydrous ethanol blends to gasoline