Honda Car Forum

Is there any advantage to running 91 octane gas in the base model RSX? I
know the type s recommends 91 octane, but the regular version only requires
87 octane. So am I just wasting my money by filling up with 91 octane??

"Jamco" <Homer@jamco.com> wrote in
news:aO_Re.252933$on1.100933@clgrps13:

> Is there any advantage to running 91 octane gas in the base model RSX?
> I know the type s recommends 91 octane, but the regular version only
> requires 87 octane. So am I just wasting my money by filling up with
> 91 octane??
>
>
>

YES.
you only need hi-octane for high compression motors.

--
Jim Yanik
jyanik
at
kua.net

In article <aO_Re.252933$on1.100933@clgrps13>,
"Jamco" <Homer@jamco.com> wrote:

> Is there any advantage to running 91 octane gas in the base model RSX? I
> know the type s recommends 91 octane, but the regular version only requires
> 87 octane. So am I just wasting my money by filling up with 91 octane??

Yes.

On Fri, 02 Sep 2005 16:08:38 GMT, "Jamco" <Homer@jamco.com> wrote:

>Is there any advantage to running 91 octane gas in the base model RSX? I
>know the type s recommends 91 octane, but the regular version only requires
>87 octane. So am I just wasting my money by filling up with 91 octane??
>
Right now you're wasting A LOT of money on premium gas. I tried a tank
of premium in my base rsx once, and couldn't tell any difference.

In article <aO_Re.252933$on1.100933@clgrps13>, "Jamco" <Homer@jamco.com> writes:
> Is there any advantage to running 91 octane gas in the base model RSX? I
> know the type s recommends 91 octane, but the regular version only requires
> 87 octane.

Other posters have already noted that there's no advantage to using
higher octane fuel than necessary. Here's a quick introduction to
octane ratings to explain why:

Gasoline is a mixture of various hydrocarbons, each with somewhat
different characteristics, including different ignition points. Since
the ignition point of a type of gasoline is important to an internal-
combustion engine (as I'll explain later), gasoline is rated as if it
were a mixture of just two hydrocarbons, hexane and octane. Hexane
has a lower ignition point than octane; octane's is close to what
most car engines would want, but a little high. The octane number
represents (in theory) the percentage of octane in a pure octane/
hexane mix that would have the same ignition point as that gasoline.

So "87 octane" gasoline ignites at about the same point as a mix of
87% octane and 13% hexane. The actual octane number, in the US, is
the average of the Motor Octane Number and the Research Octane Number
(which is why you may see the notation "(R+M)/2" on the octane
sticker), which are two standard ways of determining the octane
rating.

Why does the octane rating matter? In the cylinder, the fuel vapor
should ignite when the spark is emitted from the plug; and the burn
should propagate evenly out from the spark in a smooth wave. If the
vapor ignites prematurely (before the spark, or elsewhere in the
cylinder at the same time as the spark), you'll get less than ideal
performance - the piston may still be on the compression stroke, for
example, so the burn is forcing it the wrong way - and "knock", which
is the sound of an engine that's firing at the wrong time.

In an older engine, if you get premature ignition, you hear knocking,
get reduced performance, and risk engine damage. Newer engines have
knock sensors, and if they detect knock they'll retard the ignition
timing to compensate. That will generally eliminate the knock but
reduce performance. So using a fuel with the right octane number
will increase performance over one with too low a rating, but going
any higher won't improve things any further.

The higher the compression in the cylinder, the more likely the fuel
is to ignite, because of higher density and temperature (by Boyle's
Law). So high-compression engines need fuel with a higher ignition
point, which means a higher octane rating.

High-compression engines get more output per unit volume, but they're
more expensive (because they have to withstand higher stresses), so
they're generally found on more expensive models. Thus it's common
for more-expensive cars to take more-expensive gasoline.


--
Michael Wojcik michael.wojcik@microfocus.com

Unfortunately, as a software professional, tradition requires me to spend New
Years Eve drinking alone, playing video games and sobbing uncontrollably.
-- Peter Johnson

Michael Wojcik wrote:
> In article <aO_Re.252933$on1.100933@clgrps13>, "Jamco" <Homer@jamco.com> writes:
>
>>Is there any advantage to running 91 octane gas in the base model RSX? I
>>know the type s recommends 91 octane, but the regular version only requires
>>87 octane.
>
>
> Other posters have already noted that there's no advantage to using
> higher octane fuel than necessary. Here's a quick introduction to
> octane ratings to explain why:
>
> Gasoline is a mixture of various hydrocarbons, each with somewhat
> different characteristics, including different ignition points. Since
> the ignition point of a type of gasoline is important to an internal-
> combustion engine (as I'll explain later), gasoline is rated as if it
> were a mixture of just two hydrocarbons, hexane and octane. Hexane
> has a lower ignition point than octane; octane's is close to what
> most car engines would want, but a little high. The octane number
> represents (in theory) the percentage of octane in a pure octane/
> hexane mix that would have the same ignition point as that gasoline.
>
> So "87 octane" gasoline ignites at about the same point as a mix of
> 87% octane and 13% hexane. The actual octane number, in the US, is
> the average of the Motor Octane Number and the Research Octane Number
> (which is why you may see the notation "(R+M)/2" on the octane
> sticker), which are two standard ways of determining the octane
> rating.
>
> Why does the octane rating matter? In the cylinder, the fuel vapor
> should ignite when the spark is emitted from the plug; and the burn
> should propagate evenly out from the spark in a smooth wave. If the
> vapor ignites prematurely (before the spark, or elsewhere in the
> cylinder at the same time as the spark), you'll get less than ideal
> performance - the piston may still be on the compression stroke, for
> example, so the burn is forcing it the wrong way - and "knock", which
> is the sound of an engine that's firing at the wrong time.
>
> In an older engine, if you get premature ignition, you hear knocking,
> get reduced performance, and risk engine damage. Newer engines have
> knock sensors, and if they detect knock they'll retard the ignition
> timing to compensate. That will generally eliminate the knock but
> reduce performance. So using a fuel with the right octane number
> will increase performance over one with too low a rating, but going
> any higher won't improve things any further.
>
> The higher the compression in the cylinder, the more likely the fuel
> is to ignite, because of higher density and temperature (by Boyle's
> Law). So high-compression engines need fuel with a higher ignition
> point, which means a higher octane rating.

ok, so if that's true, how come you can't run a diesel engine on
gasoline? the compression is much higher and the adiabatic heating is
much greater in diesel engine....

>
> High-compression engines get more output per unit volume, but they're
> more expensive (because they have to withstand higher stresses), so
> they're generally found on more expensive models. Thus it's common
> for more-expensive cars to take more-expensive gasoline.

rubbish. the compression on even the most high compression si engine is
low compared to diesels. the price differential comes down to paying a
premium for "performance", but that's nothing to do with having to build
an engine that can cope with compression stress.

but doesn't the type S and non type S have the same engine? Ones just tuned
better?

"Jamco" <Homer@jamco.com> wrote in message
news:aO_Re.252933$on1.100933@clgrps13...
> Is there any advantage to running 91 octane gas in the base model RSX? I
> know the type s recommends 91 octane, but the regular version only
> requires 87 octane. So am I just wasting my money by filling up with 91
> octane??
>
>

On Mon, 05 Sep 2005 12:06:05 -0700, jim beam <nospam@example.net>
wrote:

>Michael Wojcik wrote:
>> In article <aO_Re.252933$on1.100933@clgrps13>, "Jamco" <Homer@jamco.com> writes:
>>
>>>Is there any advantage to running 91 octane gas in the base model RSX? I
>>>know the type s recommends 91 octane, but the regular version only requires
>>>87 octane.
>>
>>
>> Other posters have already noted that there's no advantage to using
>> higher octane fuel than necessary. Here's a quick introduction to
>> octane ratings to explain why:
>>
>> Gasoline is a mixture of various hydrocarbons, each with somewhat
>> different characteristics, including different ignition points. Since
>> the ignition point of a type of gasoline is important to an internal-
>> combustion engine (as I'll explain later), gasoline is rated as if it
>> were a mixture of just two hydrocarbons, hexane and octane. Hexane
>> has a lower ignition point than octane; octane's is close to what
>> most car engines would want, but a little high. The octane number
>> represents (in theory) the percentage of octane in a pure octane/
>> hexane mix that would have the same ignition point as that gasoline.
>>
>> So "87 octane" gasoline ignites at about the same point as a mix of
>> 87% octane and 13% hexane. The actual octane number, in the US, is
>> the average of the Motor Octane Number and the Research Octane Number
>> (which is why you may see the notation "(R+M)/2" on the octane
>> sticker), which are two standard ways of determining the octane
>> rating.
>>
>> Why does the octane rating matter? In the cylinder, the fuel vapor
>> should ignite when the spark is emitted from the plug; and the burn
>> should propagate evenly out from the spark in a smooth wave. If the
>> vapor ignites prematurely (before the spark, or elsewhere in the
>> cylinder at the same time as the spark), you'll get less than ideal
>> performance - the piston may still be on the compression stroke, for
>> example, so the burn is forcing it the wrong way - and "knock", which
>> is the sound of an engine that's firing at the wrong time.
>>
>> In an older engine, if you get premature ignition, you hear knocking,
>> get reduced performance, and risk engine damage. Newer engines have
>> knock sensors, and if they detect knock they'll retard the ignition
>> timing to compensate. That will generally eliminate the knock but
>> reduce performance. So using a fuel with the right octane number
>> will increase performance over one with too low a rating, but going
>> any higher won't improve things any further.
>>
>> The higher the compression in the cylinder, the more likely the fuel
>> is to ignite, because of higher density and temperature (by Boyle's
>> Law). So high-compression engines need fuel with a higher ignition
>> point, which means a higher octane rating.
>
>ok, so if that's true, how come you can't run a diesel engine on
>gasoline? the compression is much higher and the adiabatic heating is
>much greater in diesel engine....

but you have no guarenteed ignition, since theres no spark. Oh, and if
you do get igition, as you say, the compression is MUCH higher, its
likely to be premature.

>
>>
>> High-compression engines get more output per unit volume, but they're
>> more expensive (because they have to withstand higher stresses), so
>> they're generally found on more expensive models. Thus it's common
>> for more-expensive cars to take more-expensive gasoline.
>
>rubbish. the compression on even the most high compression si engine is
>low compared to diesels. the price differential comes down to paying a
>premium for "performance", but that's nothing to do with having to build
>an engine that can cope with compression stress.

flobert wrote:
> On Mon, 05 Sep 2005 12:06:05 -0700, jim beam <nospam@example.net>
> wrote:
>
>
>>Michael Wojcik wrote:
>>
>>>In article <aO_Re.252933$on1.100933@clgrps13>, "Jamco" <Homer@jamco.com> writes:
>>>
>>>
>>>>Is there any advantage to running 91 octane gas in the base model RSX? I
>>>>know the type s recommends 91 octane, but the regular version only requires
>>>>87 octane.
>>>
>>>
>>>Other posters have already noted that there's no advantage to using
>>>higher octane fuel than necessary. Here's a quick introduction to
>>>octane ratings to explain why:
>>>
>>>Gasoline is a mixture of various hydrocarbons, each with somewhat
>>>different characteristics, including different ignition points. Since
>>>the ignition point of a type of gasoline is important to an internal-
>>>combustion engine (as I'll explain later), gasoline is rated as if it
>>>were a mixture of just two hydrocarbons, hexane and octane. Hexane
>>>has a lower ignition point than octane; octane's is close to what
>>>most car engines would want, but a little high. The octane number
>>>represents (in theory) the percentage of octane in a pure octane/
>>>hexane mix that would have the same ignition point as that gasoline.
>>>
>>>So "87 octane" gasoline ignites at about the same point as a mix of
>>>87% octane and 13% hexane. The actual octane number, in the US, is
>>>the average of the Motor Octane Number and the Research Octane Number
>>>(which is why you may see the notation "(R+M)/2" on the octane
>>>sticker), which are two standard ways of determining the octane
>>>rating.
>>>
>>>Why does the octane rating matter? In the cylinder, the fuel vapor
>>>should ignite when the spark is emitted from the plug; and the burn
>>>should propagate evenly out from the spark in a smooth wave. If the
>>>vapor ignites prematurely (before the spark, or elsewhere in the
>>>cylinder at the same time as the spark), you'll get less than ideal
>>>performance - the piston may still be on the compression stroke, for
>>>example, so the burn is forcing it the wrong way - and "knock", which
>>>is the sound of an engine that's firing at the wrong time.
>>>
>>>In an older engine, if you get premature ignition, you hear knocking,
>>>get reduced performance, and risk engine damage. Newer engines have
>>>knock sensors, and if they detect knock they'll retard the ignition
>>>timing to compensate. That will generally eliminate the knock but
>>>reduce performance. So using a fuel with the right octane number
>>>will increase performance over one with too low a rating, but going
>>>any higher won't improve things any further.
>>>
>>>The higher the compression in the cylinder, the more likely the fuel
>>>is to ignite, because of higher density and temperature (by Boyle's
>>>Law). So high-compression engines need fuel with a higher ignition
>>>point, which means a higher octane rating.
>>
>>ok, so if that's true, how come you can't run a diesel engine on
>>gasoline? the compression is much higher and the adiabatic heating is
>>much greater in diesel engine....
>
>
> but you have no guarenteed ignition, since theres no spark. Oh, and if
> you do get igition, as you say, the compression is MUCH higher, its
> likely to be premature.

you cannot get premature ignition on a diesel.

>
>
>>>High-compression engines get more output per unit volume, but they're
>>>more expensive (because they have to withstand higher stresses), so
>>>they're generally found on more expensive models. Thus it's common
>>>for more-expensive cars to take more-expensive gasoline.
>>
>>rubbish. the compression on even the most high compression si engine is
>>low compared to diesels. the price differential comes down to paying a
>>premium for "performance", but that's nothing to do with having to build
>>an engine that can cope with compression stress.
>
>

On Tue, 06 Sep 2005 14:46:26 GMT, "Jamco" <Homer@jamco.com> wrote:

>but doesn't the type S and non type S have the same engine? Ones just tuned
>better?

Correct. But tuned differently is more correct than tuned better.
There are some components that are different, and the ecu is set
differently to take advantage of the components.

>
>"Jamco" <Homer@jamco.com> wrote in message
>news:aO_Re.252933$on1.100933@clgrps13...
>> Is there any advantage to running 91 octane gas in the base model RSX? I
>> know the type s recommends 91 octane, but the regular version only
>> requires 87 octane. So am I just wasting my money by filling up with 91
>> octane??
>>
>>
>