re: Octane

[Dave Conner <conner@cfm.ohio-state.edu>]

I'll tell you what know (which ain't much).

First,,,there are two different methods of measuring octane...I think they
are referred to as AKI and RON.
The 91 number in the book may not be the same index as the number you see
on the gas pump.  This depends on what country you are in.  I believe the
U.S. system is not the same one the book is referring to.

Your engine probably has an anti-knock sensor linked to the ECU and so if
you run lower octane gas no damage is done, but timing is adjusted to
eliminate knocking and performance drops.  

You may not notice this if you are not pushing the car very hard.  
In my 87 5KS with NF engine and auto trans, I do like to drive hard and I
do notice the difference.  But just how noticeable the difference is
depends on the driving I'm doing.  If I load up the family and head out
over the mountains I see a very noticeable difference in performance with
different octane gas.  This is especially noticeable when cruising on the
hills at 85 mph and trying to accelerate.  OTOH, if I'm just driving around
town here in the flatlands and in stop and go traffic the difference would
be much less noticeable.

Dave C.