At 01:02 PM 2/25/2002 -0500, you wrote:
>In my ancient experience the higher the octane produces cleaner burning
>and an increase in power. Lower octane gas in high performance engines
>will result in doing repairs sooner.
Sorry Bob, but generally speaking, this is not true the way it was
stated. The only advantage of higher octane is better resistance to engine
knock. The increase in power is accomplished by increase in the
compression ratio and/or spark advance. Now, increasing either or both of
the above parameters often requires higher octane to avoid knock. If an
engine is set up to not knock on a certain grade of fuel, running higher
octane fuel gives absolutely no benefit.
>Perhaps this is true with the lower performance engines but, remember that
>this information is from people who are in the business of selling you
>new cars.
Often, running higher octane fuel on a modern car seems to increase its
power. Because of this, people tend to think that its the "better" fuel
that gives the improved performance. In reality, modern cars have knock
sensors that automatically retard the timing when knock is encountered, and
if the "better" fuel is used, leaves the timing advanced as pre-set by the
designers . This is totally transparent to the driver, who might perceive
this as a power "loss" or "gain" due to the lower or higher octane. In our
older cars with the fixed timing, it either knocks or it doesn't!
As an added note, there are many other additives in gasoline that are
independent of octane. Modern cars with fuel injection are more sensitive
to these additives that our older engines. However, higher octane tends to
change a bit the blend of gasoline making cold start a bit harder.
D^2
Back to the Home of the Forward Look Network