Gas

["Loyd Heimbruch" <Loyd.Heimbruch@domain.elided>]

Peter from Los Angeles asked:

"All this talk about octane ratings has got me thinking.  There is a =
gas=20
station near my house that sells 103 octane, high performance gas.
Although very pricey, I've always wanted to try it.  Does high octane gas =
give a noticeable difference or would I just be throwing my money out the =
window?"

And the answer is...(this has been covered before lets not start the =
thread again)...  There is no point in using a higher octane than what is =
required to prevent engine knock.  It is a common myth that higher octane =
will produce more power.  Actually, the opposite is true.  Gasoline energy =
content is typically measured in BTU/gallon.  Octane enhancing additives =
in gasoline have less energy content than the "raw" gasoline, therefore =
reducing the total BTU/gallon of fuel mixture when they are used (since =
the fuel in is diluted by the additive).

If the octane enhancer is ethanol (used in some states), there will be =
additional changes to the fuel delivery system.  Ethanol is an oxygenate, =
in effect changing the air/fuel ratio which will cause enleanment and loss =
of power in older vehicles that do not have exhaust oxygen sensors and =
computer controlled electronic ignition.

Higher octane will allow engine modifications such as ignition timing =
changes, valve timing changes, higher compression, etc., and prevent =
engine knock.  These modifications, when used correctly to modify the =
complete system, may result in increased performance.

Loyd Heimbruch
Barnum, MN

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