Switchibg octane levels
#1
07-19-2009, 10:06 AM
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#2
07-19-2009, 10:13 AM
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07-19-2009, 10:30 AM
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07-19-2009, 12:12 PM
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07-19-2009, 04:39 PM
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#8
07-19-2009, 05:22 PM
There should be no difference in performance between 91 and 93. As a standard, premium fuel is considered 91 octane and it's the MAX available in Cali for whatever smog-**** reason they can think of. As a result, all US cars that are tuned for premium fuel use 91 octane as their benchmark. Using 93 (on a stock tuned car) will not make a difference.
#11
07-19-2009, 11:16 PM
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On cars that are made to run on 91+ octane level which pretty much they all do now, they should never run on anything lower, that's a big NO NO unless you want to kill your car's motor. It's common sense and a known fact that has been proven, the higher the grade of gasoline goes into the motor the better the engines are going to run. Higher grade gasoline's help to keep the engine to stay clean because it burns cleaner in the motor than a lower grade like say 87 or 89 which causes gunk to build up in the motor. Because of the fact that the motor has gunk in it, it now has to work harder to maintain the same power even at low rpms its still very bad. Also, your mileage all depends on your driving habits. Although, it is easier to get better mileage with a higher grade. You will notice a big difference in mileage like 53 km to 78 km difference if you are comparing an 87 or 89 to a 91 or 94 but you won't notice a difference between 91 or 94. Just maybe like 7 km to 13 km difference, nothing big. But if you keep on flooring it, the only difference you will notice is the performance. That should help some of you guys who really don't know or understand the difference between the octane grades.
But to answer (GTree5Sedan) question, yes it does matter what grade of gas you put in your car. But lets say you go to a gas station and they're out of the higher grades and all they have is 87, which does happen at times (rarely) it's okay if you put 87 in your car but instead of filling up just put a quarter or half a tank so you are not stranded and next time you fill up just put 91 or 94 to clear it up again and it won't affect your engine at all because it's not like you are always putting in 87 or 89 in your car. And personally, I've noticed that 91 shell works just as good as Sunoco's 94 in performance wise. And it doesn't really matter if your car's tuned for a higher octane, because even those cars that are made to run on 87 octane still run a lot better and even improves the longevity of the motor, if you still put higher grade gas in them.
But to answer (GTree5Sedan) question, yes it does matter what grade of gas you put in your car. But lets say you go to a gas station and they're out of the higher grades and all they have is 87, which does happen at times (rarely) it's okay if you put 87 in your car but instead of filling up just put a quarter or half a tank so you are not stranded and next time you fill up just put 91 or 94 to clear it up again and it won't affect your engine at all because it's not like you are always putting in 87 or 89 in your car. And personally, I've noticed that 91 shell works just as good as Sunoco's 94 in performance wise. And it doesn't really matter if your car's tuned for a higher octane, because even those cars that are made to run on 87 octane still run a lot better and even improves the longevity of the motor, if you still put higher grade gas in them.
Last edited by David.A.C.; 07-19-2009 at 11:21 PM. Reason: smilieys not showing
#12
07-19-2009, 11:39 PM
It's common sense and a known fact that has been proven, the higher the grade of gasoline goes into the motor the better the engines are going to run. Higher grade gasoline's help to keep the engine to stay clean because it burns cleaner in the motor than a lower grade like say 87 or 89 which causes gunk to build up in the motor. B
because even those cars that are made to run on 87 octane still run a lot better and even improves the longevity of the motor, if you still put higher grade gas in them.
I;m sorry, but that is false thinking. Higher octane gas is not "better" than 87 octane. You can't think of it in terms of the higher the number, the better the fuel. Think of it like oil, is 5W-30 better than 0w-30? No, it just depends on usage.
Same with octane. All the octane number is, is a value at which the fuel ignites. The lower the octane number, the easier and more complete the fuel burns. The higher the octane, the more resistive the fuel is to burning. That's right...87 octane burns more readily and complete than 93 octane.
However, burning easy has it's drawbacks.....detonation. With high compression engines, or older engine with carbon deposits, you might expeirence detonation when the fuel ignites before Top Dead Center. A lot of factory high compression cars run higher octanes to avoid this. So basically octane isn't making power...it's just allowing the engine to operate within it's design parameters.
I'm gonna copy/paste a post i made in another thread regarding the octane debate. Basically, it comes down to reading the manual and running the octane value recommended from the manufacturer.
Originally Posted by Mustang5L5
Read the manual. What grade gas to put in it is listed in there JUST like what grade oil. It amazed me how much research people go on different grade oils to put in their engine, but then are completely uneducated about the different octane levels of fuel.
Commercially available, you can get 85, 87, 89, 91, 93 and 94 octane. You can get higher, but i won't get into that. A few states out in the midwest at high altitudes offer 85 octane because the high altitude air is thinner and can support a lower octane without detonation.
Your engine has a recommended octane level based on a few factors. Is the engine a high compression engine? Is tuned with performance fuel and timing curves? Is there a power adder such as a turbo or supercharger? These are the factors that go into deciding what octane to run.
Octane is simply the resistance to burning a fuel is rated at. The lower the octane, the easier the fuel burns. That's it. No other difference in detergents and such within a brand. If you go to Mobil, their put the same additives in 87 octane as they do in 93 octane. The difference is the resistance to burning in an engine. Which to use depends on how the engine is engineered.
You want to run the LOWEST octane you can get away with without detonation - that marbles in a can sound you sometimes hear going up a hill. Many cars today are equipped with a KNOCK SENSOR which detects this and changes the fuel and timing to one that reduces knock. That's why the G35 says "Premium recommended" if you run 87, the knock sensor will pick up knock (if any) and reduce timing to save the engine and run safe. As a result, you may not get optimun performance.
Power adder cars usually want to run highest octane possible period, because any detonation can be fatal. So the idea is to run as big of a buffer as you can.
If your manual says your car can run safely on 87 octane (and achieve max performance) then there is no benefit to putting 93 octane in it. It's not a doggie treat for your car for years or good service. You are just wasting money. However, as years and miles go on, carbon deposits inside the engine can actually start to cause detonation even with the recommended octane level, and usually you have to step up a level to 89 octane or so. The carbon deposits retain heat and cause the fuel to pre-ignite. Good time to seafoam the engine.
With that said, the G35 recommended 91 or better for max performance. I put 93 octane in my car since 91 is tough to find.
My previous Mustang GT only required 87 octane on it's low compression V8 (8.5:1) to achieve max performance, so that's all i ever put in it. Putting 93 octane in that car would have been a waste of money.
That's the theory behind octanes, but not everyone goes along with it. You'll always have that one guy that puts 93 in everything thinking it gives him exta power and then there is the guy who just doesn't care and puts 87 octane into is SL55 even though premium is REQUIRED.
Commercially available, you can get 85, 87, 89, 91, 93 and 94 octane. You can get higher, but i won't get into that. A few states out in the midwest at high altitudes offer 85 octane because the high altitude air is thinner and can support a lower octane without detonation.
Your engine has a recommended octane level based on a few factors. Is the engine a high compression engine? Is tuned with performance fuel and timing curves? Is there a power adder such as a turbo or supercharger? These are the factors that go into deciding what octane to run.
Octane is simply the resistance to burning a fuel is rated at. The lower the octane, the easier the fuel burns. That's it. No other difference in detergents and such within a brand. If you go to Mobil, their put the same additives in 87 octane as they do in 93 octane. The difference is the resistance to burning in an engine. Which to use depends on how the engine is engineered.
You want to run the LOWEST octane you can get away with without detonation - that marbles in a can sound you sometimes hear going up a hill. Many cars today are equipped with a KNOCK SENSOR which detects this and changes the fuel and timing to one that reduces knock. That's why the G35 says "Premium recommended" if you run 87, the knock sensor will pick up knock (if any) and reduce timing to save the engine and run safe. As a result, you may not get optimun performance.
Power adder cars usually want to run highest octane possible period, because any detonation can be fatal. So the idea is to run as big of a buffer as you can.
If your manual says your car can run safely on 87 octane (and achieve max performance) then there is no benefit to putting 93 octane in it. It's not a doggie treat for your car for years or good service. You are just wasting money. However, as years and miles go on, carbon deposits inside the engine can actually start to cause detonation even with the recommended octane level, and usually you have to step up a level to 89 octane or so. The carbon deposits retain heat and cause the fuel to pre-ignite. Good time to seafoam the engine.
With that said, the G35 recommended 91 or better for max performance. I put 93 octane in my car since 91 is tough to find.
My previous Mustang GT only required 87 octane on it's low compression V8 (8.5:1) to achieve max performance, so that's all i ever put in it. Putting 93 octane in that car would have been a waste of money.
That's the theory behind octanes, but not everyone goes along with it. You'll always have that one guy that puts 93 in everything thinking it gives him exta power and then there is the guy who just doesn't care and puts 87 octane into is SL55 even though premium is REQUIRED.
#13
07-20-2009, 02:55 AM
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Reread my post and try to understand what I wrote because you misinterpreted my meaning. I never stated that the higher the octane level is the better it is. I was referring to vehicles nowadays that are made to run on higher octane levels recommended because their design is to run at high compression ratios. Yes you are right about octane levels and I know this already, because all they do is help to eliminate knocking which occurs when the air-fuel mixture in the combustion chambers ignites too early which causes knocking. Although slight knocking won’t damage your engine, loud knocking can cause damage. Which is why the higher grade gas is better because its more difficult to ignite, and that's why it burns cleaner because it's not causing early ignition in the motor. And yes, even motor's that are made to run on octane 87 still run better on higher grades of gas because with time and mileage, those vehicles began to knock as well, which is when you need to switch to the next higher octane grade to make it more difficult to ignite. And the whole topic that some people believe that a 91 octane rating gives you more acceleration over 87 octane is correct but is also false thinking. They believe higher grade gasolines are the ones that is giving the power but it's not. Nowadays, cars are built with electronic sensors in their motors that detect light knocking and eliminates it. When using a lower octane grade, the sensor works by retarding the spark which in turns reduces the acceleration of the vehicle without knocking, where as a higher octane grade could improve acceleration in this case. Hopefully, you will understand now, that I actually explained myself but it was my fault though because I should have been more clear in my explanation. Earlier.
#15
07-20-2009, 09:45 AM
