Why the high octane?

I frequently receive the following question, either on the lot, during test drives or after customers take their car home, so I thought I'd post the answer here:

Q.

If premium fuel is not used as required (according to owner's manual or fuel filler flap) what issues could be affected?

A.

The car could develop misfires, knocking (pinging) and fuel trim (lean and/or rich) faults. The higher the octane the more resistance it is to burn, hence resulting in a controlled burn. No pre-ignition. A reduction of power and fuel economy may also be noticed. Source: http://www.vwwebsource.com/fastknows/default.htm

High compression engines are programmed to run on higher octane gasoline to prevent knock.

Another helpful article on this subject can be found here: http://www.ftc.gov/bcp/conline/pubs/autos/octane.shtm.

Probably one of the best resource for VW owners is http://forums.vwvortex.com where you can search the database for the word "Octane," or anything else you've been wondering about.

Makes me think of this verse for some out of context reason:

All things are wearisome,
more than one can say.
The eye never has enough of seeing,
nor the ear its fill of hearing.

What has been will be again,
what has been done will be done again;
there is nothing new under the sun.

Is there anything of which one can say,
"Look! This is something new"?
It was here already, long ago;
it was here before our time.

-- Ecclesiastes 1:8-10