Post by Jon "bustanut" on Oct 22, 2008 23:27:56 GMT -5
High Octane Fuel vs. Low Octane Fuel : Facts and Myths
Several of us 80 series owners have been debating the use of premium vs. regular fuel and the merits of high vs. low octane fuel. Instead of high jacking the original thread where this discussion broke out, I thought we’d start a new one.
My stand is this: in a properly tuned and functioning 80 series truck, higher octane or premium fuel is a waste of money and provides no additional performance (power and mpg). In fact, it may mean a slight reduction in performance.
I’ve listed a just a FEW of the websites that I came across providing information on my position. With the facts to follow these links.
www.state.mn.us/mn/externalDocs/Commerce/Gasoline_Octane_Facts_102902052227_OctaneFacts.pdf
www.ftc.gov/bcp/conline/pubs/autos/octane.shtm
science.howstuffworks.com/gasoline3.htm
Octane Facts
• Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle
because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored
since it can result in serious damage to the engine.
• High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when
cylinder pressures are high.
• If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in
switching to higher octane gasoline.
• If your engine knocks or pings, it does not necessarily mean something is wrong with the gasoline. It could
be a problem with the engine’s electronic control systems, ignition timing or exhaust gas recirculation. On a
high mileage engine, a carbon build-up in the cylinders can increase cylinder pressures and cause knock.
• Almost all of today’s new cars have fuel-injected engines that need to use gasoline with a detergent additive.
They do not necessarily need high octane gasoline with a detergent additive. Generally, new automobiles
need high octane gasoline only if the manufacturer recommends it.
• Always follow the auto manufacturer’s octane recommendations in your owner’s manual.
Octane Myths
• High octane gasoline improves mileage.
In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve
mileage. If switching to high octane gasoline does improve mileage, you might find that your engine, or its
control systems, need repair.
• High octane gasoline gives quicker starting.
No, it doesn’t.
• High octane gasoline increases power.
If your car is designed to run on 87 octane gasoline, you shouldn’t notice any more power on high octane
gasoline. Again, if it does make a noticeable difference, your engine, or the engine’s electronic control
systems, may need repair.
• High octane gasoline has been refined more – it is just a better product.
Additional refining steps are used to increase the octane; however, these additional steps do not necessarily
make the gasoline a “better” product for all engines. They just yield a different blend of hydrocarbons that
burn more slowly. The additional steps also increase the price.
Several of us 80 series owners have been debating the use of premium vs. regular fuel and the merits of high vs. low octane fuel. Instead of high jacking the original thread where this discussion broke out, I thought we’d start a new one.
My stand is this: in a properly tuned and functioning 80 series truck, higher octane or premium fuel is a waste of money and provides no additional performance (power and mpg). In fact, it may mean a slight reduction in performance.
I’ve listed a just a FEW of the websites that I came across providing information on my position. With the facts to follow these links.
www.state.mn.us/mn/externalDocs/Commerce/Gasoline_Octane_Facts_102902052227_OctaneFacts.pdf
www.ftc.gov/bcp/conline/pubs/autos/octane.shtm
science.howstuffworks.com/gasoline3.htm
Octane Facts
• Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle
because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored
since it can result in serious damage to the engine.
• High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when
cylinder pressures are high.
• If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in
switching to higher octane gasoline.
• If your engine knocks or pings, it does not necessarily mean something is wrong with the gasoline. It could
be a problem with the engine’s electronic control systems, ignition timing or exhaust gas recirculation. On a
high mileage engine, a carbon build-up in the cylinders can increase cylinder pressures and cause knock.
• Almost all of today’s new cars have fuel-injected engines that need to use gasoline with a detergent additive.
They do not necessarily need high octane gasoline with a detergent additive. Generally, new automobiles
need high octane gasoline only if the manufacturer recommends it.
• Always follow the auto manufacturer’s octane recommendations in your owner’s manual.
Octane Myths
• High octane gasoline improves mileage.
In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve
mileage. If switching to high octane gasoline does improve mileage, you might find that your engine, or its
control systems, need repair.
• High octane gasoline gives quicker starting.
No, it doesn’t.
• High octane gasoline increases power.
If your car is designed to run on 87 octane gasoline, you shouldn’t notice any more power on high octane
gasoline. Again, if it does make a noticeable difference, your engine, or the engine’s electronic control
systems, may need repair.
• High octane gasoline has been refined more – it is just a better product.
Additional refining steps are used to increase the octane; however, these additional steps do not necessarily
make the gasoline a “better” product for all engines. They just yield a different blend of hydrocarbons that
burn more slowly. The additional steps also increase the price.
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