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93 vs 91?

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Old Dec 23, 2014 | 09:50 PM
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Default 93 vs 91?

I bought my c5 back in California, where all they have is 91 octane. The performance of the car was great, but I was still wanting more.

After getting out the military, I had sold my c5 to my father-in-law. I moved back to Texas, and now I'm watching over my ex-car for him while he's deployed. I just filled her up today with 93 octane for the first time, and OH MY GOD. I'm not sure if it's because I've been out of the car for awhile, but boy does she pull like a ****!

The question is, how big of a difference does 93 really make over 91?
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Old Dec 23, 2014 | 10:00 PM
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Im sure a lot to do with it was the fact that you've been out of the car for a while, but I recently filled up with 93 and its obvious the car responds to it.

Runs very clean and crisp , and you know youre giving the car what it wants so it feels good.

Ill be running 93 in it all the time from here on out
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Old Dec 23, 2014 | 10:44 PM
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Originally Posted by paloalto00
I bought my c5 back in California, where all they have is 91 octane. The performance of the car was great, but I was still wanting more.

After getting out the military, I had sold my c5 to my father-in-law. I moved back to Texas, and now I'm watching over my ex-car for him while he's deployed. I just filled her up today with 93 octane for the first time, and OH MY GOD. I'm not sure if it's because I've been out of the car for awhile, but boy does she pull like a ****!

The question is, how big of a difference does 93 really make over 91?
Very little if anything.
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Old Dec 23, 2014 | 11:04 PM
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Originally Posted by paloalto00
I bought my c5 back in California, where all they have is 91 octane. The performance of the car was great, but I was still wanting more.

After getting out the military, I had sold my c5 to my father-in-law. I moved back to Texas, and now I'm watching over my ex-car for him while he's deployed. I just filled her up today with 93 octane for the first time, and OH MY GOD. I'm not sure if it's because I've been out of the car for awhile, but boy does she pull like a ****!

The question is, how big of a difference does 93 really make over 91?
Octane is an additive that resists a motor's tendency to knock or pre-ignite. It has nothing to do with power output. If the octane of the fuel you are using is too low and the engine pre-ignites the ECU will pull timing until the knock goes away. This may result in lower power levels. Unless you are pulling a 5th wheel trailer or driving up a very steep incline at altitude I seriously doubt you will notice any difference between 91 and 93 octane fuel. A lot of people throw away a lot of money on high octane fuel because they think it produces more power, burns cleaner, etc. I'm not advocating using 87 or even 89 octane fuel in your Corvette but if you drive it like your DD it will run just fine and harm nothing. Having said that the compression ratio of the LS1 calls for high octane fuel and that's what I use. I've run both and driven hard with both (91 & 93) and had no issues with either. If I go a week or so between drives my car always feels quicker than I remember from the last drive. But then at my age I have trouble remembering what I had for breakfast.

Last edited by norcalace; Dec 23, 2014 at 11:07 PM.
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Old Dec 24, 2014 | 12:32 AM
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Originally Posted by Mr.Bill
Very little if anything.


Op you just haven't been in it in awhile. That's like when I drive my car for weeks in a row I'm like this thing feels slow as crap. .but when I don't drive it for a week and I get back in think ahhhhh ok now she's feels like she has 650 plus hp thought I lost boost. Point is you get use to it and a c5 really isn't that quick anymore in Stock form
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Old Dec 24, 2014 | 09:39 AM
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Unless you are adding timing to take advantage of the 93, then not much. You're probably just no longer used to the car and got a rush like when you originally drove it for the first time.

With that said, I notice a nice change when I run an E85 blend in my DD on the correct map
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Old Dec 24, 2014 | 10:44 AM
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I agree with the majority here - most likely it is just the fact you haven't driven the car in a while. I get the same feeling when I bring mine out of storage in the spring.
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Old Dec 24, 2014 | 10:46 AM
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Originally Posted by norcalace
Octane is an additive that resists a motor's tendency to knock or pre-ignite. It has nothing to do with power output. If the octane of the fuel you are using is too low and the engine pre-ignites the ECU will pull timing until the knock goes away. This may result in lower power levels. Unless you are pulling a 5th wheel trailer or driving up a very steep incline at altitude I seriously doubt you will notice any difference between 91 and 93 octane fuel. A lot of people throw away a lot of money on high octane fuel because they think it produces more power, burns cleaner, etc. I'm not advocating using 87 or even 89 octane fuel in your Corvette but if you drive it like your DD it will run just fine and harm nothing. Having said that the compression ratio of the LS1 calls for high octane fuel and that's what I use. I've run both and driven hard with both (91 & 93) and had no issues with either. If I go a week or so between drives my car always feels quicker than I remember from the last drive. But then at my age I have trouble remembering what I had for breakfast.


well stated and profound
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Old Dec 24, 2014 | 10:47 AM
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Fast cars are like women's vaginas the less you use them the better they feel
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