"Jay Honeck" wrote:

3. What is *in* that non-alcohol gas in Iowa now that boosts its
octane? TEL? MTBE? Nitroglycerine?

Iowa hasn't used MTBE for many years. Ethanol was its replacement,
and pretty well any automobile engine is allowed to use a mixture of
up to 10 percent ethanol.

So how does our "premium" gasoline (no alcohol) achieve its higher
octane?

There are differences in octane depending on where the crude oil
originally came from. Therefore, crude that has the characteristics of
higher octane can be directed to refineries that produce high octane
fuels.

Simple refineries might only have a distiller and reformer, and cannot
enhance the octane of the base fuel. They get what comes out. Therefore,
if you want even higher octane numbers, you have to process the fuel
more.

In particular, isomerization is used to boost the octane number after
base refining. That is a process that breaks up longer carbon chains
into shorter branch chains. The shorter chains have higher ignition
temperatures, and burn more slowly, which are characteristics of higher
octane fuels.

The whole refining process is a balance where they try to get the most
saleable products out of the original crude with the least left over.
They have a certain amount of ability to adjust the output between
various fuels, like diesel vs gasoline, and various octane levels,
depending on the demand.

As environmental laws have progressively limited things like sulfurs,
volotiles, butane and other compounds in the fuel, they have also tended
to lower the base octane from the normal refining processes, since those
compounds were often used to boost octane during refining. As a result,
the refineries have had to add equipment to further refine the fuels to
again push up the base octane ratings. This, of course, cost money in
capital investments, which have been recovered through higher fuel
prices.

You might remember when tetraethyl lead was no longer added to gasoline,
when "unleaded" fuel first appeared on the market, that the unleaded fuel
cost more than the original leaded fuels. This seemed a contradition to
many in that they couldn't understand why fuel price would rise when
something that had been added to fuel was no longer being added. The
answer was that the refineries had to refine the fuels further to make up
for the loss of the lead octane booster. That cost money.

Once the fuel has been refined, then octane boosters can be added to the
fuel to further raise things. The boosters can only go so far, however,
so the base fuel has to be refined sufficiently to provide the necessary
grades before the boosters are added.