What's the difference between gasoline octanes?

[ElFenix]

Originally posted by: KokomoGST

Originally posted by: WinkOsmosis
More octane makes your Honda faster.

Actually, despite WinkOzzie's facetious comment, it's actually true for some Honda engines. My friend's H22A Prelude drinks premium only... he was a clueless consumer and put regular in it... got horrible mileage, bad power, etcetc. Same deal with a friend that had bought a 2k Eclipse GT... I was like :Q
in both cases... I run only 93 in my GST, don't have the need for 94 or race gas on the tiny hairdryer.

110 Octane rating fuels such as race gasolines and other fuels (ie C-16) basically are 10% more resistant to detonation in comparison to 100% Octane fuel.

no, it was that too little octane rating was making the honda detonate or at least give the knock sensor tons of headaches.

 

[FrustratedUser]

Originally posted by: AvesPKS

Originally posted by: FrustratedUser

Originally posted by: dpk777
What makes one perform better than another?

The higher Octane fuel can deliver more power only if you increase the compression ratio or use forced induction.
Higher Octane = less prone to detonate ---> you can run higher compression which in turn gives more power.

Slightly OT but the main reason some racing series use Methanol as fuel is that Methanol has higher Octane rating (it does not contain any Octane), well above 100, so they can run higher boost and compression. At the same time the Methanol is an excellent coolant for the engine. The fresh fuel cools the intake (and the rest of the engine). The exhaust gas temperaturte is also cooler (around 300C).

If you dont believe the cooling part there is an easy way to show this. Wet your finger in alcohol. It feels really cold right!?
Do the same with gasoline. Not as cold right!?

I don't doubt that alcohol cools the engine better than gasoline, as you seem to know what you are talking about...however, (and correct me if I'm wrong), isn't the reason wetting your finger with alcohol will make it cold, is because it evaporates more quickly than gasoline, thus taking energy from your finger? And how would this have any effect inside an engine? Unless it's evaporating while it's inside...😕

You got it right. The cooling comes from evaporation. Voila! The alcohol evaporates inside the intake and the heat is taken from the metal ---> cooling.

Got you thinking and coming up with the right answer. 😀

 

[Deeko]

Originally posted by: FrustratedUser

Originally posted by: theNEOone

Originally posted by: FrustratedUser

Originally posted by: dpk777
What makes one perform better than another?

The higher Octane fuel can deliver more power only if you increase the compression ratio or use forced induction.
Higher Octane = less prone to detonate ---> you can run higher compression which in turn gives more power.

Slightly OT but the main reason some racing series use Methanol as fuel is that Methanol has higher Octane rating (it does not contain any Octane), well above 100, so they can run higher boost and compression. At the same time the Methanol is an excellent coolant for the engine. The fresh fuel cools the intake (and the rest of the engine). The exhaust gas temperaturte is also cooler (around 300C).

If you dont believe the cooling part there is an easy way to show this. Wet your finger in alcohol. It feels really cold right!?
Do the same with gasoline. Not as cold right!?

well, actually alcohol is ethanol. not methanol.

Well, actually Methanol is an alcohol too. Try it with etanol or methanol, the cooling effect feels the same and is the same effect.
The 'ol'at the end means that the HC chain contains an OH molecule instead of an H atom.


   H  H
    |   | 
H-C-C-OH               <--- Ethanol.
    |  |
   H  H


    H
    |
H-C-OH                   <--- Methanol.
    |
    H

For the sake of it we can make an alcohol with Octane, called Octanol.


   H  H   H  H  H  H   H  H
    |   |    |   |   |   |    |   |
H-C- C- C- C- C- C- C- C- OH        <--- Octanol
    |   |    |   |   |   |    |   |
   H  H   H  H  H  H   H   H

mmmm....O-Chem....

 

[Aquaman]

Originally posted by: silverpig

Originally posted by: WinkOsmosis
More octane makes your Honda faster.

But only in conjunction with a phat spoiler.

And Mugen Power Stickers 😀

Cheers,
Aquaman

 

[AvesPKS]

Originally posted by: FrustratedUser

Originally posted by: AvesPKS

Originally posted by: FrustratedUser

Originally posted by: dpk777
What makes one perform better than another?

The higher Octane fuel can deliver more power only if you increase the compression ratio or use forced induction.
Higher Octane = less prone to detonate ---> you can run higher compression which in turn gives more power.

Slightly OT but the main reason some racing series use Methanol as fuel is that Methanol has higher Octane rating (it does not contain any Octane), well above 100, so they can run higher boost and compression. At the same time the Methanol is an excellent coolant for the engine. The fresh fuel cools the intake (and the rest of the engine). The exhaust gas temperaturte is also cooler (around 300C).

If you dont believe the cooling part there is an easy way to show this. Wet your finger in alcohol. It feels really cold right!?
Do the same with gasoline. Not as cold right!?

I don't doubt that alcohol cools the engine better than gasoline, as you seem to know what you are talking about...however, (and correct me if I'm wrong), isn't the reason wetting your finger with alcohol will make it cold, is because it evaporates more quickly than gasoline, thus taking energy from your finger? And how would this have any effect inside an engine? Unless it's evaporating while it's inside...😕

You got it right. The cooling comes from evaporation. Voila! The alcohol evaporates inside the intake and the heat is taken from the metal ---> cooling.

Got you thinking and coming up with the right answer. 😀

Okay, thanks for the clarification...I did not know that. 🙂

 

[FrustratedUser]

😀

 

[BCYL]

Originally posted by: KokomoGST

Originally posted by: WinkOsmosis
More octane makes your Honda faster.

Actually, despite WinkOzzie's facetious comment, it's actually true for some Honda engines. My friend's H22A Prelude drinks premium only... he was a clueless consumer and put regular in it... got horrible mileage, bad power, etcetc. Same deal with a friend that had bought a 2k Eclipse GT... I was like :Q
in both cases... I run only 93 in my GST, don't have the need for 94 or race gas on the tiny hairdryer.

110 Octane rating fuels such as race gasolines and other fuels (ie C-16) basically are 10% more resistant to detonation in comparison to 100% Octane fuel.

That's because your friend's Prelude was designed for 92 octane gas... since he put 87 octane in it, the ECU has to retard timing to prevent detonation and damage to the engine... this in turn decreases performance...

Putting 92 octane gas in it would allow the engine to perform at the level it's supposed to perform...

 

[FrustratedUser]

The Prelude will run like crap on 87, as said ^^^^

 

[DanTMWTMP]

Originally posted by: FrustratedUser

Originally posted by: theNEOone

Originally posted by: FrustratedUser

Originally posted by: dpk777
What makes one perform better than another?

The higher Octane fuel can deliver more power only if you increase the compression ratio or use forced induction.
Higher Octane = less prone to detonate ---> you can run higher compression which in turn gives more power.

Slightly OT but the main reason some racing series use Methanol as fuel is that Methanol has higher Octane rating (it does not contain any Octane), well above 100, so they can run higher boost and compression. At the same time the Methanol is an excellent coolant for the engine. The fresh fuel cools the intake (and the rest of the engine). The exhaust gas temperaturte is also cooler (around 300C).

If you dont believe the cooling part there is an easy way to show this. Wet your finger in alcohol. It feels really cold right!?
Do the same with gasoline. Not as cold right!?

well, actually alcohol is ethanol. not methanol.

Well, actually Methanol is an alcohol too. Try it with etanol or methanol, the cooling effect feels the same and is the same effect.
The 'ol'at the end means that the HC chain contains an OH molecule instead of an H atom.


   H  H
    |   | 
H-C-C-OH               <--- Ethanol.
    |  |
   H  H


    H
    |
H-C-OH                   <--- Methanol.
    |
    H

For the sake of it we can make an alcohol with Octane, called Octanol.


   H  H   H  H  H  H   H  H
    |   |    |   |   |   |    |   |
H-C- C- C- C- C- C- C- C- OH        <--- Octanol
    |   |    |   |   |   |    |   |
   H  H   H  H  H  H   H   H

😕 😕😕😕😕😕😕😕😕😕😕😕😕

w.....t.......f.............

ANYWAYS..

it's all about EE....screw chem! hehehe 😉

 

[FrustratedUser]

U=RI owns j00!

 

You got it right. The cooling comes from evaporation. Voila! The alcohol evaporates inside the intake and the heat is taken from the metal ---> cooling.

Got you thinking and coming up with the right answer.

Only on vehicles equiped with a carburator or throttle body, port fuel injection injects the fuel directly at the back of the intake valve.

Higher Octane gasoline is harder to ignite than lower Octane gasoline, this inhibits preignition.

 

[C'DaleRider]

Originally posted by: dpk777
What makes one perform better than another?

Octane is in reality nothing more than an indication of the ability of the gasoline to resist burning.....or, in other words, adding octane booster is adding a flame retardant. The base stock is the same for all grades of gas despite what the gasoline companies tell you in their ads.


From How Stuff Works:

You know that almost all cars use four-stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. (See How Car Engines Work for details.)

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:

Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).

 

[isasir]

Skimming through this, I didn't see it posted, so I'll ask it now:

Is there a difference between getting 92 octane at a well-known place like Exxon or Mobil, as opposed to getting 92 at the mom&pop gas station down the block (or 87 at either place, for that matter)? I believe I read that Sunoco puts in fuel cleaning detergents in theirs, but I didn't know if the others don't, or how that compares.

 

[theNEOone]

Originally posted by: FrustratedUser
Well, in this case Methanol or alcohol (etahnol) doesn't matter in this case. We both know what we meant 😉

WTH is shorthand notation. I used the magic trick of the




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smiley!

shorthand: CH3OH for methanol, CH3CH2OH for ehthanol, etc.

 

[isasir]

Originally posted by: RishiS
Skimming through this, I didn't see it posted, so I'll ask it now:

Is there a difference between getting 92 octane at a well-known place like Exxon or Mobil, as opposed to getting 92 at the mom&pop gas station down the block (or 87 at either place, for that matter)? I believe I read that Sunoco puts in fuel cleaning detergents in theirs, but I didn't know if the others don't, or how that compares.

Why that's a very good question RishiS, I sure hope someone can answer it!

 

[FrustratedUser]

Originally posted by: RishiS

Originally posted by: RishiS
Skimming through this, I didn't see it posted, so I'll ask it now:

Is there a difference between getting 92 octane at a well-known place like Exxon or Mobil, as opposed to getting 92 at the mom&pop gas station down the block (or 87 at either place, for that matter)? I believe I read that Sunoco puts in fuel cleaning detergents in theirs, but I didn't know if the others don't, or how that compares.

Why that's a very good question RishiS, I sure hope someone can answer it!

No difference!
It is the same gas. The gas is pumped in pipelines and the specific additives that each brand uses are added at there distribution central.

 

[StageLeft]

Originally posted by: FrustratedUser

Originally posted by: RishiS

Originally posted by: RishiS
Skimming through this, I didn't see it posted, so I'll ask it now:

Is there a difference between getting 92 octane at a well-known place like Exxon or Mobil, as opposed to getting 92 at the mom&pop gas station down the block (or 87 at either place, for that matter)? I believe I read that Sunoco puts in fuel cleaning detergents in theirs, but I didn't know if the others don't, or how that compares.

Why that's a very good question RishiS, I sure hope someone can answer it!

No difference!
It is the same gas. The gas is pumped in pipelines and the specific additives that each brand uses are added at there distribution central.

I get the cheapest gas I can find. It's all regulated and I feel sorry for the person who pays up to $.10 more per gallon for gas from one place vs. another.

 

[isasir]

No difference!
It is the same gas. The gas is pumped in pipelines and the specific additives that each brand uses are added at there distribution central.

I get the cheapest gas I can find. It's all regulated and I feel sorry for the person who pays up to $.10 more per gallon for gas from one place vs. another.

Cool. I thought I read somewhere tho' that I should continually try to use the same company's gas, as opposed to jumping around whomever is the cheapest that week.

 

[Quixfire]

Originally posted by: RishiS

No difference!
It is the same gas. The gas is pumped in pipelines and the specific additives that each brand uses are added at there distribution central.

I get the cheapest gas I can find. It's all regulated and I feel sorry for the person who pays up to $.10 more per gallon for gas from one place vs. another.

Cool. I thought I read somewhere tho' that I should continually try to use the same company's gas, as opposed to jumping around whomever is the cheapest that week.

That's right, your mileage will be more constant than if you switch to the cheapest producer every time you need to fill up.

 

[FrustratedUser]

Originally posted by: Quixfire

Originally posted by: RishiS

No difference!
It is the same gas. The gas is pumped in pipelines and the specific additives that each brand uses are added at there distribution central.

I get the cheapest gas I can find. It's all regulated and I feel sorry for the person who pays up to $.10 more per gallon for gas from one place vs. another.

Cool. I thought I read somewhere tho' that I should continually try to use the same company's gas, as opposed to jumping around whomever is the cheapest that week.

That's right, your mileage will be more constant than if you switch to the cheapest producer every time you need to fill up.

Says who?
If the mileage do vary, it is probably in the 10's of a % so it really doesn't matter.

 

[Wolfie]

Originally posted by: AAjax
I fear in many cases only the nozzel its pumped out of. After working at a gas station in high school I never wasted my $$ on "higher" octane. Many stations fill all the tanks with the same stuff 🙁

This is not LEGAL! If you think they where filled with the same stuff, you maybe refering to the the tanker that delivers it. But the tankers have seperate compartments on one tanker. 🙂

BUT, a lot of stations mix the 87 with 92 to make 90 or 89 octane. The pumps do the mixing. It is actualy mixed this way at the refineries. Oh, and depending on your location also makes a difference on what your car needs. Example: In Montana and certin parts of North Dakota you can find 85 Octane. Your car doesn't need the higher octane at higher altitudes. Just a tip for you that think your car NEEDS a certin Octane.

It doesn't matter where you get your gas tho. It all comes from the same place. Example: Here in St. Paul/Minneapolis there is Three different places that refine the gas. Two places in Roseville and one in Newport. The truckers are told wich place to go depending on price. So one time it could come from Roseville. The next time from Newport. But they are all mixed the same. So it doesn't matter what station you go too.

Oh, and to see how smart you guys are, what is the highest octane rating? 😀

Wolfie