Octane ratings vs power
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Heel & Toe
Joined: Jan 2010
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From: Norfolk
Octane ratings vs power
I understand higher octane reduces the chances of detonation and increases engine output (marginally).
Am I right to assume 'premium' grade in the US is 91octane?
In the UK our normal unleaded is 95octane and the Shell V-Power (£1.18 a litre!) is 99octane.
What kind of improvements would this show on a rolling road?
In previous cars I've owned liked evo's & impreza's this has made up to 10bhp difference and that's on a car with a stock 280bhp.
Am I right to assume 'premium' grade in the US is 91octane?
In the UK our normal unleaded is 95octane and the Shell V-Power (£1.18 a litre!) is 99octane.
What kind of improvements would this show on a rolling road?
In previous cars I've owned liked evo's & impreza's this has made up to 10bhp difference and that's on a car with a stock 280bhp.
Le Mans Master
Joined: Nov 2005
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Use what the owners manual says. Higher octane in a stock engine does nothing but waste money.
Octane is a measure of how volitile the fuel is, the HIGHER the number the LESS volitile the fuel is. That's why you use higher octane to stop detonation, it's HARDER to ignite a HIGHER octane fuel so it's less likely to ignite in a hot cylinder before an ignition spark and cause a gas engine to preignite/diesel.
Octane is a measure of how volitile the fuel is, the HIGHER the number the LESS volitile the fuel is. That's why you use higher octane to stop detonation, it's HARDER to ignite a HIGHER octane fuel so it's less likely to ignite in a hot cylinder before an ignition spark and cause a gas engine to preignite/diesel.
Le Mans Master
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The higher the boost/effective compression ratio, the easier it is the cause detonation since the heat in the cylinder is so much higher. That's why you need higher octane fuel as compression ratios go up. Forced Induction is like raising compression ratio, your Pre-compressing what's going in.
Le Mans Master
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From: CA.
St. Jude Donor '13-'14-'15
In todays computer controlled engines--running better fuel is always a good idea---Even though you may not hear any pinging or detonation--the Knock sensors are so sensitive in these cars the ECM will pull timing over aggressively at times for a slight hint of pinging or for no reason at all---These cars tyically only have about 18-20* timing at WOT so if the ECM is taking out 3-4 * for a probable ping then you are losing over 10% of your timing--
97-2000 vettes are known to have bad knock sensors-Best way to see whats going on is of course to run some data logging--this often explains why sometimes your car runs like a striped ape and other times it is a dog from a dead stop--It's losing timing via the knck sensors---
In an older car with a carb and points --this is not true however--It is an old wives tale that better fuel will make more power without an adjustment manualy to the timing
the car has no way of removing or adding timing on is own--
97-2000 vettes are known to have bad knock sensors-Best way to see whats going on is of course to run some data logging--this often explains why sometimes your car runs like a striped ape and other times it is a dog from a dead stop--It's losing timing via the knck sensors---
In an older car with a carb and points --this is not true however--It is an old wives tale that better fuel will make more power without an adjustment manualy to the timing
the car has no way of removing or adding timing on is own--
Tech Contributor
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From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
You're comparing apples and pears unfortunately
In the US the gas is rated in PON or Pump Octane Number
93/94 is premium, 91 is mid grade and 87 is low grade. Gas is mixed at the pump.
In UK we use RON
In UK, 95 equates to 91 in the US and 99 equates to about 94.
I use Regular (95) most of the time because its all I can get at many petrol stations in Lincolnshire, although I'd use Super (99) out of preference. I've don't have pinging even WOT. Shell V Power is good and I use it when I can get it as it also has a fuel additive that might prevent the dreaded gas gauge problems.
In the US the gas is rated in PON or Pump Octane Number
93/94 is premium, 91 is mid grade and 87 is low grade. Gas is mixed at the pump.
In UK we use RON
In UK, 95 equates to 91 in the US and 99 equates to about 94.
I use Regular (95) most of the time because its all I can get at many petrol stations in Lincolnshire, although I'd use Super (99) out of preference. I've don't have pinging even WOT. Shell V Power is good and I use it when I can get it as it also has a fuel additive that might prevent the dreaded gas gauge problems.
Last edited by DeeGee; Jan 13, 2010 at 03:35 PM.
Race Director
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From: Raleigh, NC
St. Jude Donor '15
You aren't hearing pinging bc the computer will pull timing faster than you can hear it.
Not saying you'd really notice a difference..but it's more than likely happening.
Not saying you'd really notice a difference..but it's more than likely happening.
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Tech Contributor
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From: Horncastle Lincolnshire, England
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UK gas is higher octane than US gas. Pinging isn't an issue. No pinging even in Vegas in Summer and the best I could get was 91
Last edited by DeeGee; Jan 13, 2010 at 03:33 PM.
Race Director
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St. Jude Donor '15
Oh, I thought you were saying the UK numbers, while higher numerically, are actually comparable to what the US has..just rated differently
So, when you say "regular" I thought you meant it was basically the same as what regular 87 octane is here in the states.
Apparently I can't read today
So, when you say "regular" I thought you meant it was basically the same as what regular 87 octane is here in the states.
Apparently I can't read today
Tech Contributor
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From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
Oh, I thought you were saying the UK numbers, while higher numerically, are actually comparable to what the US has..just rated differently
So, when you say "regular" I thought you meant it was basically the same as what regular 87 octane is here in the states.
Apparently I can't read today
So, when you say "regular" I thought you meant it was basically the same as what regular 87 octane is here in the states.
Apparently I can't read today
Don't worry; divided by a common language
And I would never use 87
even if it was on sale
Melting Slicks
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Team Owner
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From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
As far as the "power" output of an engine, think of higher octane this way: All else being equal, it doesn't make horsepower. It merely keeps you from losing what you already have. A bit over simplistic maybe, but accurate.
For a given engine, anything more than what is necessary to eliminate knock (uncontrolled explosion basically), is a waste of money. Running higher octane than a particular engine needs doesn't "hurt" it (as some people think), it is just, as I said, a waste of money.
I prefer, and run, 93 octane. Even when I still had my stock LS1 I ran 93 as it is widely available all over Texas.
For a given engine, anything more than what is necessary to eliminate knock (uncontrolled explosion basically), is a waste of money. Running higher octane than a particular engine needs doesn't "hurt" it (as some people think), it is just, as I said, a waste of money.
I prefer, and run, 93 octane. Even when I still had my stock LS1 I ran 93 as it is widely available all over Texas.
Tech Contributor
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E-T who is a retired Corvette Engineer involved in the design of the car has strong views on octane. I agree strongly on this one. Thanks to timemender for the links.
http://forums.corvetteforum.com/show....php?t=1845445
Our testing on the use of sub octane fuel ( 87 octane ) we always found that # 7 cylinder was the first to exhibit some failure, be it a ring or the top of the piston, connecting rod bearing or wrist pin. I'M not saying that you were using 87 octane fuel but this is the typical outcome of the use of 87 octane. I’ve tried to point this out a dozen times over the years, and those who think this is a fluke, or I don’t know what I'M talking about...a cracked ring can be very costly in the face of detonation, under any circumstance. So using 87 octane just puts your engine at risk...use it all the time and you can knock off 100,000 miles of trouble free driving. Those who advocate the use of 87 octane fuel could have been the reason this member lost a cylinder.
I am very sorry for the grief with your car...and hope things work out with the least amount of stress possible.
Bill aka ET
AND ALSO this –
http://forums.corvetteforum.com/show....php?t=1973285
................................... Because the LS1/2 is a high compression engine, 10.5 :1 it requires high octane gas. The lowest being 91 octane, but even that in the summer might require octane booster,, while it does say you can use 87 octane and the car won’t break, but it is not recommended for this motor. It’s just to get you to the next gas station. Using this fuel will cause detonation under load. The knock sensors detect knock, this knock detection is caused by engine knock... the detection causes a timing change, but the engine is knocking before this change occurs. This knocking causes connecting rod bearing failure, and wrist pin damage over time. Severe cases we have seen holes burnt right through pistons, predominantly Piston # 7, when using regular gas over a long period of time.
ET aka Bill (Evil-Twin)
Team Owner
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From: Raleigh / Rolesville NC
but finding sunoco 94 is hard to do.