100 Octane vs 91 Octane ???
Thread Starter
Racer
Joined: Sep 2005
Posts: 484
Likes: 0
From: Redwood City CA
100 Octane vs 91 Octane ???
I live in Nor. Cali. and pay the Highest $$$ in the nation for gas, I pay $ 3.60 a gallon....I pulled into a 76 station today and saw that they sell 100 Octane @ $ 5.30 a gallon. Any-Way, my question is ---
1) Would I benefit from a higher octane ?
2) If so, How ?
3) If I would benefit would it be better to mix 91 w/100, saw half & half,
or run straight 100 ???
As you can see I run basically stock except the headers, but new Lt4 hot cam w/roller rockers are planed this year along with a port & polishing of the heads, must keep it sniffer approved....
I'm all
on this guys.....
1) Would I benefit from a higher octane ?
2) If so, How ?
3) If I would benefit would it be better to mix 91 w/100, saw half & half,
or run straight 100 ???
As you can see I run basically stock except the headers, but new Lt4 hot cam w/roller rockers are planed this year along with a port & polishing of the heads, must keep it sniffer approved....
I'm all
on this guys.....
Melting Slicks
Joined: Oct 2000
Posts: 3,426
Likes: 4
From: Heidelberg PA
Cruise-In V Veteran
Simply - no.
You want to use the lowest octane available that your car runs great on (no knock). Higher octane burns slower & is usually required for highly modified engines.
On the street I run 93, but at the track I do run an average of 100 octane for full throttle runs.
You want to use the lowest octane available that your car runs great on (no knock). Higher octane burns slower & is usually required for highly modified engines.
On the street I run 93, but at the track I do run an average of 100 octane for full throttle runs.
Race Director
Joined: Oct 2001
Posts: 19,653
Likes: 426
From: Melbourne Florida
Cruise-In IV Veteran
I agree..higher octane fuels burn slower because they are harder to detonate...this is why some may recommend a couple of gallons of 100 octane in your tank if you are having detonation problems...higher compression ratio's call for higher octane as well...puting it in a stock motor car will actually decrease your power and fuel economy...
Like 85 vet said...do not do it...
Like 85 vet said...do not do it...
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The ONLY thing higher octane gasoline provides, is greater knock resistance than the lower octane gases. If you aren't experiencing knock, go a grade lower. Keep going lower until you experience knock, and then go back up the previous, non-knocking level. More octane than needed ONLY wastes money. There are no "hidden" benefits.
RACE ON!!!
RACE ON!!!
Le Mans Master
Joined: May 2005
Posts: 7,309
Likes: 2,231
From: Central Maryland
The ONLY thing higher octane gasoline provides, is greater knock resistance than the lower octane gases. If you aren't experiencing knock, go a grade lower. Keep going lower until you experience knock, and then go back up the previous, non-knocking level. More octane than needed ONLY wastes money. There are no "hidden" benefits.
RACE ON!!!
RACE ON!!!
If your ECM is capable of retarding spark timing based upon input from knock sensors, you'd be ill-advised to keep going lower with the octane until you develop spark knock, because you never will hear it -- but your performance will suffer as a result of the retarded spark timing.
Be well,
SJW
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Racer
Joined: Aug 2004
Posts: 371
Likes: 0
From: California Missouri
100 Octane hold on to your CATS
Guys,, I know this has already been decided but when I used to run that stuff in the 67, it was my understanding that it had Lead or some type of substitute in it that would kill your CATS. I do know that it left some kind of crazy white residue all over the back of the car. Just wondered if most racing gas has that stuff in it.
Drifting
Joined: Nov 2002
Posts: 1,905
Likes: 1
From: 2003 Points Champ Great Lakes Corvette Challenge; 2006/2007 Winner MSD True Street
Guys,, I know this has already been decided but when I used to run that stuff in the 67, it was my understanding that it had Lead or some type of substitute in it that would kill your CATS. I do know that it left some kind of crazy white residue all over the back of the car. Just wondered if most racing gas has that stuff in it.
As a person whose car ONLY runs on 100 octane, let me chime in.
100 octane is UNleaded and labeled as such on the pump.
You may find as high as 104 unleaded.
110, 116, 119 are ALL leaded and will kill your cats and your O2 sensor most likely.
Matt383
Racer
Joined: Aug 2005
Posts: 469
Likes: 1
very interesting guys!!!!
hi there guys,
i was always running high octane 98 rating fuel in my 1991 L98 vette thinking it was better as in more performance and better quality fuel!
this 98 fuel here in australia by shell and mobil and bp say that this particular fuel was also designed to help clean fuel system and help clean the motor with its cleaning higher quality fuel agents!!!
here in australia we have
91 octane standard
preium unleaded 94 octane
98 performance cleaning higher octane
and then off course avgas aviation fuel 104 octane which is hard to get now!
so after reading this now i shall use the preium 94 octane instead of the 98 rating fuel and see how we go!
in 1991 L98 engine what compression ratio does this motor run in standard form any way please?
i heard that it is 10:5:1 ratio??
any way thanks for your advice and help guys!!!
cheers
glen
Australia
i was always running high octane 98 rating fuel in my 1991 L98 vette thinking it was better as in more performance and better quality fuel!
this 98 fuel here in australia by shell and mobil and bp say that this particular fuel was also designed to help clean fuel system and help clean the motor with its cleaning higher quality fuel agents!!!
here in australia we have
91 octane standard
preium unleaded 94 octane
98 performance cleaning higher octane
and then off course avgas aviation fuel 104 octane which is hard to get now!
so after reading this now i shall use the preium 94 octane instead of the 98 rating fuel and see how we go!
in 1991 L98 engine what compression ratio does this motor run in standard form any way please?
i heard that it is 10:5:1 ratio??
any way thanks for your advice and help guys!!!
cheers
glen
Australia
Pro
Joined: Nov 2006
Posts: 638
Likes: 0
From: Plano TX
Guys,, I know this has already been decided but when I used to run that stuff in the 67, it was my understanding that it had Lead or some type of substitute in it that would kill your CATS. I do know that it left some kind of crazy white residue all over the back of the car. Just wondered if most racing gas has that stuff in it.
Pro
Joined: Dec 1999
Posts: 673
Likes: 0
From: Venetia,Pa,USA
I heard so much BS concerning octane and if used with advanced timimg would generate additional HP. Well, My engine is a ZZ4 crate motor[10:1 compression] with a Comp Cam and roller rockers so since I need dyno pulls for my NASA race class I thought I'd give it a try. In March I bought [$58/5gal] some 103 octance racing fuel. I made a number of pulls with the 93 I normally run; then add the 5 gals. of 103 which made a 98 octane mixture in my tank. Ran the engine a while to mix the fuel and made three more pulls at more advance. GUESS what not 1 HP improvement. In fact with too much advance lost me HP. SOOOO just stick with 93 unless you like to spend money.I'm sure if a engine was running 11:1 or higher would benefit from additional octane.
Drifting
Joined: Nov 2002
Posts: 1,905
Likes: 1
From: 2003 Points Champ Great Lakes Corvette Challenge; 2006/2007 Winner MSD True Street
I heard so much BS concerning octane and if used with advanced timimg would generate additional HP. Well, My engine is a ZZ4 crate motor[10:1 compression] with a Comp Cam and roller rockers so since I need dyno pulls for my NASA race class I thought I'd give it a try. In March I bought [$58/5gal] some 103 octance racing fuel. I made a number of pulls with the 93 I normally run; then add the 5 gals. of 103 which made a 98 octane mixture in my tank. Ran the engine a while to mix the fuel and made three more pulls at more advance. GUESS what not 1 HP improvement. In fact with too much advance lost me HP. SOOOO just stick with 93 unless you like to spend money.I'm sure if a engine was running 11:1 or higher would benefit from additional octane.
Higher octane for higher compression.
100 octane in stock compression designed for 92 octane is a waste.
On another note 100 octane here is not like the "cleaning" octane down under.
100 octane has a reputation for being "dirty".
SOooo I use STP gas treatment with my 100 octane as well.
I do use TORCO octane additive (NOT a "booster") and can make 100, 104, up to 110 by following the mixing directions on the can with 93 pump gas.
383
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by SJW
Quote:
Originally Posted by CFI-EFI
The ONLY thing higher octane gasoline provides, is greater knock resistance than the lower octane gases. If you aren't experiencing knock, go a grade lower. Keep going lower until you experience knock, and then go back up the previous, non-knocking level. More octane than needed ONLY wastes money. There are no "hidden" benefits.
RACE ON!!!
All true. But...
If your ECM is capable of retarding spark timing based upon input from knock sensors, you'd be ill-advised to keep going lower with the octane until you develop spark knock, because you never will hear it -- but your performance will suffer as a result of the retarded spark timing.
Be well,
SJW
Originally Posted by CFI-EFI
The ONLY thing higher octane gasoline provides, is greater knock resistance than the lower octane gases. If you aren't experiencing knock, go a grade lower. Keep going lower until you experience knock, and then go back up the previous, non-knocking level. More octane than needed ONLY wastes money. There are no "hidden" benefits.
RACE ON!!!
All true. But...
If your ECM is capable of retarding spark timing based upon input from knock sensors, you'd be ill-advised to keep going lower with the octane until you develop spark knock, because you never will hear it -- but your performance will suffer as a result of the retarded spark timing.
Be well,
SJW
RACE ON!!!
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Racer
Joined: Dec 2006
Posts: 325
Likes: 2
From: Chattanooga TN
if you are climing long steep grades, perhaps, but WOT on level grades at high altitudes shouldnt need any higher octane. in fact, it should lower your octane requirement some.
Cruising
Joined: Mar 2007
Posts: 11
Likes: 0
From: Göteborg, Sweden