Octane road test
Thread Starter
Pro
Joined: Dec 2004
Posts: 674
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From: Daytona Beach Florida
Octane road test
So, a couple of weeks ago I got a full tank of 87octane gas(sunoco). The vette ran like crud(like it was missing a cylinder). Well, with my hectic life, I forgot that I got the 87oct. A few days later I bought a fuel pressure gauge, because It felt like I was either losing fuel press. or spark. Fuel pressure checked out fine. So, onto the spark. I checked the wires for arcing in the dark, none. Ohmed them hot and cold. I was almost out of gas by this point, and that's when I remembered, I got the crappy gas. So, I filled up w/ my normal super prem., I think it's 93(Texaco). Dang vette is running like it's brand new. The only difference is the gas I put in it. I was just amazed at the night and day difference. It was a worthwhile effort because I know for sure the difference in gas. I always believed there was minimal difference between regular and premium. Now I know better.
Team Owner
Joined: Sep 2002
Posts: 22,209
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From: OBAMA IS HITLER
you're wasting $$ on a full tank of 93 octane. 91 is considered optimal (although often hard to find) for a 10.25:1 car.
what i do is mix 1/2 each 89 and 93 octanes, since 91 is hard to find.
what i do is mix 1/2 each 89 and 93 octanes, since 91 is hard to find.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Bubba91
So, a couple of weeks ago I got a full tank of 87octane gas(sunoco). The vette ran like crud(like it was missing a cylinder).
I filled up w/ my normal super prem., I think it's 93(Texaco). Dang vette is running like it's brand new.
I filled up w/ my normal super prem., I think it's 93(Texaco). Dang vette is running like it's brand new.
RACE ON!!!
Melting Slicks
Joined: Aug 2003
Posts: 3,378
Likes: 388
From: Lakeville MI
I recently tried a tank of Sunoco 89 octane and my car knocked like crazy, clearly audible knocks, and knock counts would take off on just about every moderate to heavy throttle.
After that it was back to 93 for me. I think I have a fairly rich tune and conservative timing, but there was no denying the knocks on 89 octane.
After that it was back to 93 for me. I think I have a fairly rich tune and conservative timing, but there was no denying the knocks on 89 octane.
Safety Car
Joined: Oct 2002
Posts: 3,991
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From: Phoenix AZ
It can also be the motor. My car used to knock bad in the WINTER when I ran Sunoco Ultra 94 When I ripped the motor apart the piston tops were coverd in a nasty buildup, up to 1/8" in some places! So it may be the fuel or it could be something else if some cars knock on 87 Octane and some don't. You may want to look deeper.
Here is a pic of one of the piston tops.
Here is a pic of one of the piston tops.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by tequilaboy
I recently tried a tank of Sunoco 89 octane and my car knocked like crazy, clearly audible knocks, and knock counts would take off on just about every moderate to heavy throttle.
Originally Posted by stubbs
It can also be the motor. My car used to knock bad in the WINTER when I ran Sunoco Ultra 94
Originally Posted by Bubba91
So, a couple of weeks ago I got a full tank of 87octane gas(sunoco). The vette ran like crud(like it was missing a cylinder).
RACE ON!!!
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
Originally Posted by CFI-EFI
You guys didn't read the opening post very carefully.
His complaint wasn't of knocking or detonation, which can be caused by low octane, but one of missing, which has nothing to do with octane. It was an invalid test with a Kopbett conclusion.
RACE ON!!!
His complaint wasn't of knocking or detonation, which can be caused by low octane, but one of missing, which has nothing to do with octane. It was an invalid test with a Kopbett conclusion.
RACE ON!!!
There, I fixed it for you.
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Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
Originally Posted by Hot Rod 90
you're wasting $$ on a full tank of 93 octane. 91 is considered optimal (although often hard to find) for a 10.25:1 car.
what i do is mix 1/2 each 89 and 93 octanes, since 91 is hard to find.
what i do is mix 1/2 each 89 and 93 octanes, since 91 is hard to find.
My '89 runs great on a mix.
Thread Starter
Pro
Joined: Dec 2004
Posts: 674
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From: Daytona Beach Florida
Originally Posted by CFI-EFI
You guys didn't read the opening post very carefully.
His complaint wasn't of knocking or detonation, which can be caused by low octane, but one of missing, which has nothing to do with octane. It was an invalid test with a Bubba conclusion.
RACE ON!!!
His complaint wasn't of knocking or detonation, which can be caused by low octane, but one of missing, which has nothing to do with octane. It was an invalid test with a Bubba conclusion.
RACE ON!!!
I don't see where you got invalid test from though.
1. I ran the car with a full tank(87), until it was almost empty.(it ran horrible)
2. I ran the car after the next fill up(93). It was instantly better.
therefore--- My problem was the gas.
That's called deductive reasoning. If the premises are true, then the conclusion has to be true. (Socrates)
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
I'll bet that your first tank of gas had more of a problem than octane. A close friend of mine in South Florida owns 11 gas stations and has told me many times that they sometimes get a bad load in a tank. The reason he knows is because many people come back to complain.
Team Owner
Joined: Jun 2001
Posts: 26,196
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From: Orlando FL
St. Jude Donor '08-'09
I've tried 87 2 times in the 7 years I've had my 89... both times it ran like absolute garbage. It didn't have its getup and go, it sounded like it was missing once in a while, the gas milage was terrible.
So I always put 93 in it. Never have a single problem with that grade.
So I always put 93 in it. Never have a single problem with that grade.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
Originally Posted by Bubba91
I'm not sure what you mean by "Bubba conclusion". I accept there may have been water in the gas, but whatever the reason, the car ran bad w/ the 87 and great with the 93. My name is Bubba and that was my conclusion; so, I guess you were right.
I don't see where you got invalid test from though.
1. I ran the car with a full tank(87), until it was almost empty.(it ran horrible)
2. I ran the car after the next fill up(93). It was instantly better.
therefore--- My problem was the gas.
That's called deductive reasoning. If the premises are true, then the conclusion has to be true. (Socrates)
I don't see where you got invalid test from though.
1. I ran the car with a full tank(87), until it was almost empty.(it ran horrible)
2. I ran the car after the next fill up(93). It was instantly better.
therefore--- My problem was the gas.
That's called deductive reasoning. If the premises are true, then the conclusion has to be true. (Socrates)
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Bubba91
I don't see where you got invalid test from though.
1. I ran the car with a full tank(87), until it was almost empty.(it ran horrible)
2. I ran the car after the next fill up(93). It was instantly better.
therefore--- My problem was the gas.
1. I ran the car with a full tank(87), until it was almost empty.(it ran horrible)
2. I ran the car after the next fill up(93). It was instantly better.
therefore--- My problem was the gas.
Originally Posted by Bubba91
That's called deductive reasoning. If the premises are true, then the conclusion has to be true. (Socrates)
Once again, the octane rating of any gasoline will not cause an engine to miss or run poorly.
RACE ON!!!
Thread Starter
Pro
Joined: Dec 2004
Posts: 674
Likes: 1
From: Daytona Beach Florida
Originally Posted by CFI-EFI
And that is where you should have quit. How or why do you attribute the poor running with any one characteristic of the gasoline? Maybe it was the "Sunoco purple" vs the orange colored Texaco gas. Maybe it had to do with which way the car was facing when you fueled it. Whatever the cause, there is no way it could have been the octane of the gasoline. The title to the thread is "Octane road test". Your test is no more a test of octane than it is a test of how cars run that are filled on Thursdays vs Mondays, or whatever days might be involved. Of course you have ruled out the phases of the moon from your "deductive reasoning", right?
Pick a premise, any premise. You have a red car. Your car ran poorly on Sunoco gas. Therefore all red cars will run poorly on Sunoco gas. I don't think so. "If the premises are true, then the conclusion has to be true. (Bubba)".
Once again, the octane rating of any gasoline will not cause an engine to miss or run poorly.
RACE ON!!!
Pick a premise, any premise. You have a red car. Your car ran poorly on Sunoco gas. Therefore all red cars will run poorly on Sunoco gas. I don't think so. "If the premises are true, then the conclusion has to be true. (Bubba)".
Once again, the octane rating of any gasoline will not cause an engine to miss or run poorly.
RACE ON!!!
You're right, I don't really have any proof. I was just being defensive.
Nice one.
Burning Brakes
Joined: Jul 2005
Posts: 758
Likes: 6
From: Gainesville, FL
Originally Posted by Hot Rod 90
you're wasting $$ on a full tank of 93 octane. 91 is considered optimal (although often hard to find) for a 10.25:1 car.
what i do is mix 1/2 each 89 and 93 octanes, since 91 is hard to find.
what i do is mix 1/2 each 89 and 93 octanes, since 91 is hard to find.