What octane do you use?
Melting Slicks
Joined: Dec 2014
Posts: 2,788
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From: Central UT
I live at 5k feet altitude (home is at 6500), and the highest octane we can get here is 91, which I use. When we road trip it, always get the highest octane we can find - usually 93 at lower altitudes. I'll never try and save a few $ by running a lower octane. As others have stated, owners manual says you can run lower if necessary, but you'll get lower performance and potential 'knocking'. And if you know what 'knocking' really is, you won't chance it. 
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Joined: Apr 2016
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So the owner's manual calls for a minimum of 91. Here in California that's the highest you can get. So you're always filling your tank with the minimum recommended. Is there any significant benefit with 93... performance? engine life? Should 91folks consider supplementing? Also, how precise is the octane measurement in gas? Are refiners allowed some deviation?
AIR FORCE VETERAN
Joined: Nov 2009
Posts: 6,223
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From: Pennsylvania
Octane, by itself, does not make power. Some think that increased octane carries with it more power like percentage of nitro. Higher octane allows the engine to maximize the tune. The anti knock sensors add timing until they sense knock. The higher octanes allow more ignition lead. The increased igniton timing makes more power. Higher octanes burn slower so you can hit them with spark sooner without pre ignition . Since 91 is such a good number going to 93 will make more horsepower and torque but by percentage it is not a big deal. Colder intake air could be just as effective. E85 is a whole different deal. Probably the biggest increase . Alcohol has 50% of the power of gasoline per gallon but you can increase the volume and make power because alcohol cools combustion chamber better then gasoline allowing tuning to make more power.
I use Sunoco 93. Works for me and I get .05% off every dollar I spend for gas. Retirement deal.
I use Sunoco 93. Works for me and I get .05% off every dollar I spend for gas. Retirement deal.
Last edited by Bill17601; Apr 25, 2016 at 08:02 PM.
Racer
Joined: Nov 2009
Posts: 278
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From: Arnegard ND
Worse performance? Without flex fuel I would run out of fuel shy of 700hp. Have you looked into what you are saying at all????
Melting Slicks
Joined: Sep 2009
Posts: 2,180
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From: Minnetrista Minnesota
Octane, by itself, does not make power. Some think that increased octane carries with it more power like percentage of nitro. Higher octane allows the engine to maximize the tune. The anti knock sensors add timing until they sense knock. The higher octanes allow more ignition lead. The increased igniton timing makes more power. Higher octanes burn slower so you can hit them with spark sooner without pre ignition . Since 91 is such a good number going to 93 will make more horsepower and torque but by percentage it is not a big deal. Colder intake air could be just as effective. E85 is a whole different deal. Probably the biggest increase . Alcohol has 50% of the power of gasoline per gallon but you can increase the volume and make power because alcohol cools combustion chamber better then gasoline allowing tuning to make more power.
I use Sunoco 93. Works for me and I get .05% off every dollar I spend for gas. Retirement deal.
I use Sunoco 93. Works for me and I get .05% off every dollar I spend for gas. Retirement deal.
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Joined: Jun 2007
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From: Bel Air (by way of Fort Worth, TX) Maryland
St. Jude Donor '12 thru '21
So the owner's manual calls for a minimum of 91. Here in California that's the highest you can get. So you're always filling your tank with the minimum recommended. Is there any significant benefit with 93... performance? engine life? Should 91folks consider supplementing? Also, how precise is the octane measurement in gas? Are refiners allowed some deviation?
Octane levels explained
https://en.m.wikipedia.org/wiki/Octa...nal_variations
In a nutshell, the reason you don't need more than 91 octane in higher elevations is because even for a high compression engine such as the ones in Corvettes the engine isn't sucking in as much air(oxygen) per cycle and doesn't require the extra octane to prevent knocking, or more accurately, detonation.
Last edited by Chemdawg99; Apr 26, 2016 at 06:19 AM.
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Joined: Jun 2007
Posts: 66,409
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From: Bel Air (by way of Fort Worth, TX) Maryland
St. Jude Donor '12 thru '21
Octane, by itself, does not make power. Some think that increased octane carries with it more power like percentage of nitro. Higher octane allows the engine to maximize the tune. The anti knock sensors add timing until they sense knock. The higher octanes allow more ignition lead. The increased igniton timing makes more power. Higher octanes burn slower so you can hit them with spark sooner without pre ignition . Since 91 is such a good number going to 93 will make more horsepower and torque but by percentage it is not a big deal. Colder intake air could be just as effective. E85 is a whole different deal. Probably the biggest increase . Alcohol has 50% of the power of gasoline per gallon but you can increase the volume and make power because alcohol cools combustion chamber better then gasoline allowing tuning to make more power.
I use Sunoco 93. Works for me and I get .05% off every dollar I spend for gas. Retirement deal.
I use Sunoco 93. Works for me and I get .05% off every dollar I spend for gas. Retirement deal.
The bolded is an old wives tale that gets repeated so often that people actually believe it. The octane number of a fuel has zero correlation to its flame speed. The octane number is purely a measure of a fuel's resistance to knock and nothing more. In actuality, a slower flame speed increases the tendency for knock to occur.
There are some high octane race fuels blended to burn very fast for use in 500 cu in, 10,000 RPM Pro-Stock engines but you can put the same fuel in an engine happy on 87 octane and go faster in the 1/4 mi with reduced timing...it's all about reducing negative work.
There are some high octane race fuels blended to burn very fast for use in 500 cu in, 10,000 RPM Pro-Stock engines but you can put the same fuel in an engine happy on 87 octane and go faster in the 1/4 mi with reduced timing...it's all about reducing negative work.
From previously posted link:
Octane rating or octane number is a standard measure of the performance of an engine or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating (igniting). In broad terms, fuels with a higher octane rating are used in high performance gasoline engines that require higher compression ratios.
Melting Slicks
Joined: Mar 2013
Posts: 3,104
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From: Baton Rouge LA
It averages out to be ~91 octane, which is the car's spec, so it saves about 20-30¢/gal. every other fill-up and there have been no issues. I know, I have a $70k car, etc., etc. No need to go there.
Used this procedure with the C6, too, also with no issues. If the tank is more than a bit below 1/2 I use 93 octane regardless.
Used this procedure with the C6, too, also with no issues. If the tank is more than a bit below 1/2 I use 93 octane regardless.
Last edited by iclick; Apr 26, 2016 at 02:52 PM.
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Joined: Jun 2007
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From: Bel Air (by way of Fort Worth, TX) Maryland
St. Jude Donor '12 thru '21
It averages out to be ~91 octane, which is the car's spec, so it saves about 20-30¢/gal. every other fill-up and there have been no issues. I know, I have a $70k car, etc., etc. No need to go there.
Used this procedure with the C6, too, also with no issues. If the tank is more than a bit below 1/2 I use 93 octane regardless.
Used this procedure with the C6, too, also with no issues. If the tank is more than a bit below 1/2 I use 93 octane regardless.
Seems to be an awful lot of trouble to go to to save a little bit of money, but to each his/her own.