The truth about gasoline

[GMMerlin]

Here is some info about gasoline


A number of myths about octane have grown over the
years. There is a widespread perception that the greater the
octane the better the performance. However, once enough
octane is supplied to prevent engine knock, there is little, if
any, performance improvement. One exception to this would
be in vehicles equipped with knock sensors. In these vehicles,
if octane is insufficient, the computer will retard the timing to
limit engine knock. If the vehicle is operating in the “knock
limiting” mode (retarded timing), using a higher octane fuel will
allow timing to be advanced, resulting in some level of
performance increase. However, even in these vehicles,
tests have shown that there is no perceptible performance
improvement from using a fuel of higher octane than that
recommended by the vehicle manufacturer.
Another myth is that using a higher octane fuel will result
in improved fuel economy (increased miles per gallon). Octane
is nothing more than a measure of anti-knock quality.
Fuel economy is determined by a number of variables including
the energy content of the fuel. Some premium grades of
fuel may contain components which increase energy content.
In those cases, fuel economy may improve slightly as a result
of higher energy content, but not as a result of the higher
octane. Two fuels of identical octane could have different
energy content due to compositional differences.
Consumers need only use a gasoline meeting the
vehicle manufacturer’s recommended octane levels. If engine
knocking occurs on such fuels and mechanical causes
have been eliminated, then the consumer should purchase
the next highest octane gasoline (above the manufacturer's
recommendation in the owners manual) that will provide
knock-free operation.

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[blazee]

Good post, I've seen a lot of people spreading those myths.

There is some more good info about gasoline here:
http://www.faqs.org/faqs/autos/gasoline-faq/part1/

If you want to skip to the part about octane:
http://www.faqs.org/faqs/autos/gasoline-faq/part3/

[dmbrisket 51]

best way to think of it, its the way the professor said it to us, and thats what made it click for me. If octain, in fact does give a benifit, then why, when you go to the races they are running 110 or 114 octain at the most? you can get up to 160 octain, but it has no benifit, and, the higher the octain the slower it burns, sounds backasswords but it is true, the advantage to high octain is if you have a valve not sealing correctly, the slower burning high octain will burn off carbon