As I've pointed out... and the linked article above clearly states...
There is no "end all, be all" answer. Reading the FULL article is strongly suggested. My wife's GZ seems to run hotter than others with the standard spark plug. Particularly in the summer, her bike will knock in lower RPMs while accelerating. Running 91 octane in her bike stops it. Every time I've put 87 in it, it knocks.
All things considered? I run 91 on her bike. A little as its ridden and as little cost for her bike, its small insurance. The article also makes several references to the differences between "old engines and modern engines". While the GZ is relatively modern, it is also relatively old. An air cooled and carbuerated engine.. and while i may be wrong, I think the ignition advance is fairly static? That article suggests that if knock is experienced, you should experiment with fuels until you achieve a no-knock result and then stick with it.
It has its purposes, but using a higher octane fuel is not exactly a performance enhancer.
Running a HIGHER octane fuel should do no more damage than a minimum rated fuel. However, running a LOWER ocane rating than called for COULD lead to damage from engine knock. (or as stated in my wife's bike which tends to knock with 87) A particular brand of fuel is usually formulated the same across the board with the octane rating being the primary divider among them... until you get into "cleaning agents" and other additives.
A reference from the above-listed article:
Quote:
6.14 Does low octane fuel increase engine wear?
Not if you are meeting the octane requirement of the engine. If you are not
meeting the octane requirement, the engine will rapidly suffer major damage
due to knock. You must not use fuels that produce sustained audible knock,
as engine damage will occur.
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.... and another quote (slightly dumbed down) from another article:
http://www.edmunds.com/fuel-economy/...g-premium.html
Quote:
Smarter Engines Protect Themselves
If you're still in doubt about switching to a lower-octane fuel, here's a deeper explanation of why the change is unlikely to hurt your car.
First of all, premium gas is more expensive because it contains a higher percentage of octane. Why is this important? When vaporized gas mixes with air and fills the combustion chamber, it is compressed by the rising pistons. This makes the gas-air mixture grow hot and it could ignite before the spark plug fires, pushing backward on the piston. Higher-octane fuels can be compressed to a greater degree without self-igniting. That's why premium gas is used in high-performance engines.
In the old days, engines could not adjust to fuels with varying octane ratings. Use the wrong fuel and the engine would knock or "ping" audibly because the gas exploded prematurely. This knocking damaged internal engine components over time.
Today, engine control systems can compensate for low octane by monitoring knock activity and adjusting ignition advance to avoid knocking. This sophisticated electronic capability effectively tunes the engine on the fly and gives drivers more flexibility in the grade of fuels that they can safely use.
Compared to premium gasoline, lower-octane fuels don't allow the engine to run as much ignition advance during situations calling for rapid acceleration. More ignition advance allows the engine to make more power, and accelerate more quickly, during these conditions. Since the engine doesn't make quite as much power with lower-octane fuels, this translates into slower acceleration in cars for which premium fuel is recommended. The performance loss is especially noticeable in turbocharged gasoline engines, which have become increasingly popular in recent years.
The performance loss, however, is something you will only notice if you have a heavy foot and accelerate rapidly from a dead stop or while changing lanes at highway speeds. But if you accelerate moderately, the loss of power is barely noticeable, regardless of whether you use premium or regular-grade fuel.
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