>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.
Not really, with proper fuel it is not "normal" to knock at all.
>. High octane gasoline burns slower than low octane gasoline. The slow burn
>prevents engine knock when cylinder pressures are high.
Somewhat true, while it does burn a bit slower it also has a higher
auto ingition temp too
>. 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.
Not true at all in a modern computer control engine with knock
detection as it will quell knock by retarding spark before you hear it
and make you falsely beleive that you are feeding it correctly while
steal power effeciency and MPG. The ONLY reason there is a knock
sensor is to limit consumer complaints on low octane fuel because many
still beleive the 87 octane is the holy grail of fuels and the best to
use.
>. 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.
Somewhat true but if you increase octane you will get rid of knock and
if you change timing or other cotrol to reduce peak pressure and temp
to quell knock you reduce overall efficency too.
>. 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.\
This is wrong, they will all benifit from higher octane fuel,
especailly in warmer weather or towing. The only reason that owner
manual say 87 (and it does say minimum not the best possible) is
because to state 89 or better would be a sales killer for those that
are stuck on the holy grail of fuels hence the reason for the knock
sensor.
>. Always follow the auto manufacturer's octane recommendations in your owner's
>manual.
Take some of them with a grain of salt because all EPA MPG tests are
performed with 93 octane, not 87 but you will not find that in manual
either.
>Octane Myths
>
[quoted text clipped - 4 lines]
>might find that your engine, or its
>control systems, need repair.
Pure BS. Where do you get this crap? Every car I have bought in the
last 15 year runs better and gets better MPG with 89 or better gas. I
have a 89 suburb 4x4 that I bought new and it was a slug on a hot day
with A/C and 87 octane when new and wanted to kncok some because not
even knock control could control it completely. I have been running 93
in it for over 12 years now and it runs great!! Daughters Saturn is a
slug on hot day with 87 octane but with 93 is is a different animal.
The list goes on I do not use 87 octane in any of my cars but you can
believe what you want too.
>. High octane gasoline gives quicker starting.
>No, it doesn't.
Sometimes it can if engine is hot and it is auto igniting and making
cranking difficult
>. 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.
Again BS. Your modern engine is designed to tolerate it and nothing
more because there will always be those that will use the cheapest gas
they can find.
>. 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.
Not really true. Engine CR and load cycle and climate has a big input
on octane requirements of fuel and you are suggestion that 100LL or
110 avgas is not good stuff. BTW most small A/C engine are low CR and
they require 100LL because they know that you need good octane to get
best possible power out of a engine because there is not room for
knocking or pinging in flight nor for power loss from knock control.
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TheSnoMan.com
SC Tom - 13 Sep 2006 11:18 GMT
>>. High octane gasoline improves mileage.
>>In general, if your car is designed to run on 87 octane gasoline, high
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> The list goes on I do not use 87 octane in any of my cars but you can
> believe what you want too.
I used to run 89 in my cars because I DID get better mileage, and there
seemed to be a noticeable difference in power. But when I tried that with my
'02 Escape V6, I found that running a higher octane made no difference
except in my wallet. I got 20-21MPG around town with both fuels, and 25-26
on the highway. I haven't tried 93 because I think it would be cost
prohibitive, but if the prices keep dropping, I might.
The only real difference I've noticed was the time I tried Enmark (10%
ethanol). My mileage dropped by more than 15% around town, and there was a
noticeable lack of power. I ran 3 tankfuls just to let the computer get used
to it, but went right back to my old brand when there was no improvement.
SC Tom
SnoMan - 13 Sep 2006 12:50 GMT
>I used to run 89 in my cars because I DID get better mileage, and there
>seemed to be a noticeable difference in power. But when I tried that with my
[quoted text clipped - 6 lines]
>noticeable lack of power. I ran 3 tankfuls just to let the computer get used
>to it, but went right back to my old brand when there was no improvement.
It is not unusual for MPG to drop with E10 or E15 because of lower
energy content. Also sometimes you have to force ECM's to work with
better fuel by removing ECM fuse for about a minute and putting ECM
back into learn mode
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TheSnoMan.com
SC Tom - 16 Sep 2006 15:40 GMT
>>I used to run 89 in my cars because I DID get better mileage, and there
>>seemed to be a noticeable difference in power. But when I tried that with
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> TheSnoMan.com
I have tried that with the Escape when switching octanes, but it didn't have
any different results. I'm not complaining, though- the vehicle gets
reasonable mileage (to me), and has all the power I need.
SC Tom
SnoMan - 16 Sep 2006 16:08 GMT
>I have tried that with the Escape when switching octanes, but it didn't have
>any different results. I'm not complaining, though- the vehicle gets
>reasonable mileage (to me), and has all the power I need.
My GM vehicle and a Jeep cherokee I have all do better power and MPG
wise with better fuel. I never buy 87 for my vehciles no matter what
the fuel cost is.
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TheSnoMan.com