For those that don't like to read, here's a quick quote:
MTBE is an oxygenate, so is ethanol. Aromatics are toxic additives that
increase the octane rating of gas, which the EPA wants reduced because of
the emissions they cause.
"Oxygenates that are added to gasoline function in two ways. Firstly they
have high blending octane, and so can replace high octane aromatics in the
fuel. These aromatics are responsible for disproportionate amounts
of CO and HC exhaust emissions. This is called the "aromatic substitution
effect". Oxygenates also cause engines without sophisticated engine
management systems to move to the lean side of stoichiometry, thus reducing
emissions of CO ( 2% oxygen can reduce CO by 16% ) and HC ( 2% oxygen can
reduce HC by 10%) [17], and other researchers have observed similar
reductions also occur when oxygenates are added to reformulated gasolines
on older and newer vehicles, but have also shown that NOx levels may
increase, as also may some regulated toxins [18,19,20].
However, on vehicles with engine management systems, the fuel volume will
be increased to bring the stoichiometry back to the preferred optimum
setting. Oxygen in the fuel can not contribute energy, consequently the
fuel has less energy content. For the same efficiency and power output,
more fuel has to be burnt, and the slight improvements in combustion
efficiency that oxygenates provide on some engines usually do not
completely compensate for the oxygen."
After reading, MTBE is not an anti-freeze agent. It's a pollution control
additive :)
Mike
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