The Truth About Gasoline

Here is some info about gasoline


A number of myths about octane have grown over the
years. There is a widespread perception that the greater the
octane the better the performance. However, once enough
octane is supplied to prevent engine knock, there is little, if
any, performance improvement. One exception to this would
be in vehicles equipped with knock sensors. In these vehicles,
if octane is insufficient, the computer will retard the timing to
limit engine knock. If the vehicle is operating in the “knock
limiting” mode (retarded timing), using a higher octane fuel will
allow timing to be advanced, resulting in some level of
performance increase. However, even in these vehicles,
tests have shown that there is no perceptible performance
improvement from using a fuel of higher octane than that
recommended by the vehicle manufacturer.
Another myth is that using a higher octane fuel will result
in improved fuel economy (increased miles per gallon). Octane
is nothing more than a measure of anti-knock quality.
Fuel economy is determined by a number of variables including
the energy content of the fuel. Some premium grades of
fuel may contain components which increase energy content.
In those cases, fuel economy may improve slightly as a result
of higher energy content, but not as a result of the higher
octane. Two fuels of identical octane could have different
energy content due to compositional differences.
Consumers need only use a gasoline meeting the
vehicle manufacturer’s recommended octane levels. If engine
knocking occurs on such fuels and mechanical causes
have been eliminated, then the consumer should purchase
the next highest octane gasoline (above the manufacturer's
recommendation in the owners manual) that will provide
knock-free operation.

go HERE for more info (http://www.e85fuel.com/forsuppliers/changes_in_gasoline.pdf)

Good point did you ever hear of cars driving on hemp oil?

Since you brought this up, I think I might add to it on the economic level... gas prices.

First things first, say goodbye to cheap gas because it is gone for good. Just a part of history. Why is that you might ask? Do the middle eastern countries hate us? Probably, but that's no reason to not sell us oil for fair prices. Is our world running out of oil? Hardly. In fact, geologists say that we're not even at the 50% depletion mark yet. There's plenty to go around, but the fact is that the "easy oil" is gone. Whatevers left in the oil reservoirs is becoming increasingly harder to extract. It costs a great deal more money to extract oil really deep within the Earths surface, and they compensate for that cost by... you guessed it... raising prices on the oil. That's one of the major factors in gas prices going higher, but what contributes to it the most is probably the massive economic boost of the two gargantuan nations in our world: China and India. These two countries are building like there's no tomorrow, and due to the size of the nations and their populations of over 1 billion people each, they are consuming mind boggling amounts of oil. Then there's the war in Iraq, which we all know about.

Anyway, fact is, unless we cut down on our oil consumption, gas prices will not go down. Instead they will go up. At this rate, expect it to be in the $4 maybe $5/gallon range very soon.

Theoretically, if all vehicles in the USA were to improve their economy by just 1 mile per gallon, our daily gas consumption would drop down by approx. 1.5 billion gallons. Leave that monster in the garage tonight. ;)

I've heard that using higher octane is better (on the long run) for the health of your engine. I don't exactly know what 'health' entails, but I've heard that using high octane gas extends the life of the engine. Is there any truth to that?

Yeah, that can be true. Some gasolines have a higher concentration of cleaners in their Premium grades. Just like Shell. As far as I know, the Premium grade of Shell has that V-Power.

I disagree, using higher octane than what the engine needs has no benefits other than making your wallet lighter. I'm not so sure I buy any of these gas gimmicks either, like V-Power ot Techron. There might be something there, but I doubt its worth the extra money. I buy the cheapest gas I can find. IMO, gas is gas.

As I know, the octane number only indicate how fast the gas will burned.
While there are another factor about the quality of the gas, energy. How much the energy is released when the fuel is burned.
Using higher octane number than the engine's need is wasting money, but higher energy could do something, but the air/gas ratio must be re-adjust.
Also, the fuel should contain some kind of lubricants (if needed by the engine) for lubricating the exhaust valve.

Andy

As I know, the octane number only indicate how fast the gas will burned.
While there are another factor about the quality of the gas, energy. How much the energy is released when the fuel is burned.
Using higher octane number than the engine's need is wasting money, but higher energy could do something, but the air/gas ratio must be re-adjust.
Also, the fuel should contain some kind of lubricants (if needed by the engine) for lubricating the exhaust valve.

Andy


Octane is gasolines resistance to combustion. The higher the octane number the higher the the resistance. The air/fuel mixture in some engines can be ignited prematurely by number of factors. Overheating, advanced timing, high compression, hot carbon contaminates....etc. In a normally functioning engine, the only reason for higher octane fuel is for engines with higher compression. Higher octane fuel only provides a power boost over lower octane fuel when the lower octane fuel is pre-igniting. The "energy" in gasoline is the same over all grades and brands. The lubricant in gasoline (lead) has long been eliminated with the advancement of hardened valve seats.

Fact: Although the higher octane in premium fuels may not effect the engine (yea, yea, except in knock) there are certain premium fuels that have excellent additive packeages that can really help an engine. Most of these additives are types of dergents that help clean carbon deposits off valves and combustion surfaces.

Fact: the octane number is reached by the (R+M)/2 method. You may have seen this on the gas pump, if not look sometime. The fuel is tested in a variable compression, single cylinder engine. It is tested in the research method (I believe at 1000 rpm) and and then in the motor method (I believe at 2000 rpm). These numbers are then added and diveded by two (averaged). The numbers come into play by increasing the compression until knock is acheived.

I forget how they derive the number from the compression setting, but the higher the number, the higher the resistance to detonation, not the resistance to combustion. We want the fuel to combust, but not controlled.

I am sure somebody will inform me of the actual rpm numbers, and i am sure somebody else is going to knock the detergent part, go ahead, you're retarded.

I am not disagreeing with any of you, but why would they sell 100 octane unleaded and 110 leaded race fuels at the Shell station down the street if they only reduce knocking? Please don't say because they know that someone's gonna buy it.

He's got a point, I've bought cheap 85 OCT gas and my car worked fine. So wondering the difference I purchased the expensive 91 or 93 OCT gas and i swear my car accelerated faster and got more MPG, i don't know if it was better for the environment or not but i know the performence results.

I am not disagreeing with any of you, but why would they sell 100 octane unleaded and 110 leaded race fuels at the Shell station down the street if they only reduce knocking? Please don't say because they know that someone's gonna buy it.
If you look most of those stations with 100 or 108 or even 110 on the street have a pump to can rule. Most wont allow pump to car filling.



The higher octanes such as racing fuels AND aviation fuels are for higher compression engines that require alot of timing.

If you use too much of a high octane that is not recomended for said engine it can screw alot up.


They do help reduce knocking especially with these engines(race) that run so close to detonation.

The "energy" in gasoline is the same over all grades and brands.

There is more energy available in lower octane fuel. At least that's what I was taught in college. I imagine that has something to do with the torque capabilities of diesel engines.

They sell those higher octane fuels (100, 110) for two reasons. One, some older cars around the time where lead was popular in gas need them. Two, some idiots will actually buy high octane gas they don't need. Lead was an additive that boosted the octane rating severely. They could take gas that wasn't even 87 octane, add lead, and it'd perform like octane in the 90's. And by perform, I mean resist uncontrolled combustion. Putting 92 octane in an engine that requires 87 octane makes no difference at all. Overall the Octane rating is just a percentage of octane in the gas. Octane is a carbon chain of 8 carbons. Now you'll be like "How can you have more than 100 percent octane?" And I'll answer, go back to high school chemisty. Well, seriously, there is nonane, 9 carbons, decane, 10, and so on up to 12 that is used in gasoline. The longer chains are less common; however, 1 percent of the longer chains (higher than octane) count as more than 1 percent octane, because they resist uncontrolled combustion a lot better.

As for detergents... Ok premium gasolines do have detergents, which can help engine performance, because they also tend to lubricate the upper cylinder, and all the fuel injection/carb parts. BUT, the amount you pay for that in 5 gallons, is enough for you to run to Advance Auto Parts and buy Red Line fuel injector cleaner to do the same thing for 100 gallons. Just get what you're car needs 87 or w/e, and then go and buy you're own additives if you really want them.

All Right, it seems we have to break this down barney style for you. Once again, octane number is representative of a fuels resistence to detonation. The previous post concerning octane being a hydrocarbon molecule with eight carbons and blah blah blah is true. The purpose of these high octane fuels is generally for racing. In a racing aplication you crank up the ignition advance, boost compression and do lots of other things that would normally destroy an engine without the proper octane fuel.

What is the difference between 89 and 93 octane at the pump? Not much other than a little higher octane and possibly some addative packages, detergents and what not.

Does your car need it? I don't know, if your edecated enough to be able to get on this forum and type something you can probably look it up in your owners manual.

...basically what I just said :-\

Since you brought this up, I think I might add to it on the economic level... gas prices.

First things first, say goodbye to cheap gas because it is gone for good. Just a part of history. Why is that you might ask? Do the middle eastern countries hate us? Probably, but that's no reason to not sell us oil for fair prices. Is our world running out of oil? Hardly. In fact, geologists say that we're not even at the 50% depletion mark yet. There's plenty to go around, but the fact is that the "easy oil" is gone. Whatevers left in the oil reservoirs is becoming increasingly harder to extract. It costs a great deal more money to extract oil really deep within the Earths surface, and they compensate for that cost by... you guessed it... raising prices on the oil. That's one of the major factors in gas prices going higher, but what contributes to it the most is probably the massive economic boost of the two gargantuan nations in our world: China and India. These two countries are building like there's no tomorrow, and due to the size of the nations and their populations of over 1 billion people each, they are consuming mind boggling amounts of oil. Then there's the war in Iraq, which we all know about.

Anyway, fact is, unless we cut down on our oil consumption, gas prices will not go down. Instead they will go up. At this rate, expect it to be in the $4 maybe $5/gallon range very soon.

Theoretically, if all vehicles in the USA were to improve their economy by just 1 mile per gallon, our daily gas consumption would drop down by approx. 1.5 billion gallons. Leave that monster in the garage tonight. ;)


1.) The price of gasoline was hardly affected when the price of oil went to over $70.

2.) Why was this? what is causeing the price of gasoline to be so high is the refineries. There hasnt been a new refinery built in many years and some of the major ones for the south where destroyed during katrina.

3.) Oil isnt getting so much harder to extract...the drillers just arent extracting it, causing a demand which raises oil prices which (if the refineries where doing their job and wherent being shut down by tree huggers) would lower the price of gasoline, diesle, kerosine, and alot of other things.

4.) If the echo freaks would allow drilling off the coast of florida and more in alaska we would have 0 problems. Instead the echo freaks are fighting to have alternative fules made (i have nothing agianst that, ALWAYS have a backup plan) while they drive the price of the current fule up by protesting to retstict it so much.

Solution to all our problems? Ship all echo freaks to france while thoes of us with our heads screwed on right work on accesing current fules while creating alternatives.

This is 2nd hand, but a guy at work has a car that is built to run on 87 octane, and it has a knock sensor. The station was out of regular, so he got premium at the regular price. I suggested this is a great time to check if premium helps. On his 1 tank experience, he got about a 5% improvement in economy, but with our premium at 10% more, it's obviously not worth it.
I may buy some premium for a long trip, to get the better mieage, but also for a nice long drive with more cleaners in the fuel.

The octane rating of a fuel is only a measurement on the fuels resistance to detonation. Nothing else! Octane rating of a fuel is measured in Cooperative Fuels Research single cylinder variable compression test engine. That engine is equipped with sensors which can register knock intensity, it also has a four bowl carburettor so you easily can switch between the test sample and the reference fuels. The two common reference fuels are n-heptane at 0 and n-octane at 100. With octane racings above 100, n-octane with tetra ethyl lead added is the common reference, but at very high octane ratings other references may be needed. This do however mean that the octane scale is not completely linear.

In general there is no need to buy a fuel with a higher octane rating than the manufacturer recommends, but sometimes it may be needed, for example if the outside temperature is very high or the octane rating of the fuel is uneven (poor quality).

Cars using knock sensors have an ideal ignition timing. Using the recommended fuel, the engine can usualyl be run at such an ignition timing. So there is no benefit in using a higher octane. Benefits of higher octanes are usually imaginary.

Gas is not gas! Even if the octane rating is the same there may be differences. However, in most cases the gasoline within a certain area is similar since the same fuel and supply chain are mostly used. Fuel of lower quality can have inpurities, contain high levels of sulfur, smaller amounts of additives.

Fuels such as Shell V-Power is a "designer fuel". It's not a normal refinery product but a blended fuel using many different refinery products of different composition. This makes the fuel a bit better, but at a higher cost.

Crude oil isn't the only "raw material" for gasoline and diesel. It may also be produced from coal, biomass and various gases using Fischer-Tropsch. However, today the crude oil price is still too low for this to be an economic success. Using gases is the simplest method, biomass and coal must first be converted into a gas and to do that without soot isn't that simple. Today, for example Shell sells diesel fuel where a part of the fuel is made from gas.
In the future fuels produced from sources such as coal will put a limit on the crude oil price, and also on how much oil is worth to extract. Coal is very cheap and it is availible in large amounts, but the conversion is today costly. Coal and other possible raw materials is in general availible in most western countries.

Big deal about octane...

Some of us have older cars. Like my Chevelle for example. If I drive it on 87 octane, when I accelerate the valves make horrendous noises. Some of you might hear the little clatter noises when you go up hills?? This is from using 87 and sometimes 89 octane. Depends on the car. When I fill with 93 I have no problems and yes there is a far better run with the 93.

My wifes 93 Olds Silhouette. 275,000 and the inside is spotless. Again, 87 Octane and the valves clatter when going up the hills or trying to accelerate. Go back to 93 and it stops. Do you notice your valves clattering? You wonder what that noise is when you go up a hill? Open your window and listen to your engine once.

I use my 95 Olds to and from work. Thats about it. 87 and I get about 280-300 miles to the tank. 93 and its upwards about 350-400. I did have a tank goto 417 awhile back.

WHY some of you might think theres no change is because you are going from 93 and then filling your tank with 89-87. This is not a tank of true 87-89. This is a couple of gallons (5) of 93 mixed with 10-15 gallons of 87-89...making like 90-91. To get true 87-89 use it for 3-4 tank fulls. Then you will have a true tank of 87-89.

Will I use anything less then 93? Nope. Is there a difference IMO. YES. Is there a shortage? Not necessarily a shortage more like waking up... I was in Iraq for a year and just returned home in June. I also did a convoy up through Iraq from Kuwait and I counted convoy after convoy of Oil trucks going the other direction. 30-40 truck per convoy. The reason arabic countries are raising the prices is because they are becoming knowledgable in our demands. We continue to use more and more. Iraq holds 10% of the Earths entire oil supply. Think about it. You know how Americans are... You deny me I will take...

Octane is just octane. If you need it , it IS a big deal. If you do not then it is a non-issue.

There are normally "Minimum Octane requirements" as long as the minimum is met then that's what's important.

Using a higher octane to remedy an engine issue (i.e. valve clatter) is just a band aid solution, it's not a fix to the problem. Also, I don't know how octane has any relationship with valve clatter, octane is a resistance to combustion (piston knock), how can that affect valve clatter? Does anyone know?

Detonation is being mistaken for valve clatter.

Thats what I figured was happening.

Yes, octane rating is the resistance to detonation. With a higher number, the car can advance it's timing, and increase fuel economy. It's worked on every car that I could change the timing on, but now I have to let the computer do it.

Pretty good write-up from Federal Trade Commission on this, for those who are still not convinced:
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

Yes, octane rating is the resistance to detonation. With a higher number, the car can advance it's timing, and increase fuel economy. It's worked on every car that I could change the timing on, but now I have to let the computer do it.

I can go along with that. Would my 95 blazer obd2 automatically adjust timing up? I kinda doubt it.

Now that I think about it, I am wondering if any cars are normally "on the edge" od detonation enough that they are relying upon the knock sensor for timing control?

In other words the timing is not normally being retarded because of knock sense so that increase in octane will not advance timing any.

My '85 VW was automatically adjustable. It ran well on hitest (recommended), but it wouldn't knock on regular, just not as quick and worse mileage.
I think anything with a knock sensor would adjust, but I could be wrong.

In other words the timing is not normally being retarded because of knock sense so that increase in octane will not advance timing any.
Yes, this is almost exactly how any car comes tuned from the factory.
There is always an optimum timing in terms of power and efficiency(mileage), and every car is designed and tuned so it uses this optimum timing on recommended gas without detonation. To make most out of the engine, detonation zone starts just a couple of degrees off the optimum timing when using recommended fuel.

the truth about gasoline is for ca people it has mtv-e in it and its going to give us all cancer becuase of lame-*** nafta. sick!

Now that I think about it, I am wondering if any cars are normally "on the edge" od detonation enough that they are relying upon the knock sensor for timing control?

In other words the timing is not normally being retarded because of knock sense so that increase in octane will not advance timing any.

The factory computer sets an optimum ignition curve. It leaves it fully advanced to that point unless it senses detonation. So, if your owner's manual recommends 87 and you put 93 in, it won't continue to advance, it will just use the default map in the memory.

So, no more power or economy will come from more octane unless something is out of whack with the engine. As a normal operational thing, a stock engine will rarely retard ignition on the recommended fuel.

Yes, octane rating is the resistance to detonation. With a higher number, the car can advance it's timing, and increase fuel economy. It's worked on every car that I could change the timing on, but now I have to let the computer do it.

Advancing the timing past optimal lead for your combination will hurt power and most likely economy with it. If your car makes best power on a dyno at 35* total advance with 87 octane, switching it to 37* and 93 octane will lower power. The key there is flame front. Since you haven't changed the flame front speed, you build too much pressure 2 degrees sooner in the chamber, meaning the rising piston has to fight more pressure. The result is lower power.

Proper advance doesn't change with octane, its fixed given the mechanical operating parameters of the engine. This is the exact reason why you need ENOUGH octane and adding more won't make more power.

Adding more octane won't "let" the computer do anything. It won't go past optimum lead. You have to physically program the computer for more timing, which, like I said, will most likely hurt power and economy. The right combo is the best combo. More is not better.

Curious.
My VW GTI required premium fuel. The manual said it would run on regular, but at reduced power.
An old car with breaker points, I could manually advance the timing with premium, and get better mileage, but that timing would would cause knocking if I put regular in it. And that really hurt performance.
My present car, the manula suggests premium if I'm towing, or using the car in very hot weather.

Curious.
My VW GTI required premium fuel. The manual said it would run on regular, but at reduced power.
An old car with breaker points, I could manually advance the timing with premium, and get better mileage, but that timing would would cause knocking if I put regular in it. And that really hurt performance.
My present car, the manula suggests premium if I'm towing, or using the car in very hot weather.

Exactly what I was saying with the VW... its timing curve, compression, and other properties are optimized for premium. Reducing octane kicked in the knock sensors, retarded ignition, and reduced power.

Conversely, my 73 454 is optimized for 87. If I advance the timing and run 93 it just knocks and pings because the flame front is smacking the top of the piston way too early. Power and economy suffers greatly. I'm using more of the crank's rotation fighting the early ignition.

All I can suggest on the points car is that it was timed conservatively in order to prevent overheating, reduce NOx, or it was an HD application where detonation was a potential problem

And your present car... they're just covering their butts on warranty repairs in case you're one of those tow drivers that just puts their foot to the floor and hopes :)

Interesting discussion, but I like to make a comment.

a stock engine will rarely retard ignition on the recommended fuel.
The thing with the ecu is that is programmed in a room with a constant temperature and constant humidity. In normal driving conditions the ecu will retard ignition. High temperatures, heavy load or high altitude have influence on the combustion. So using fuel with a higher octane number can increase power. Or like BMW likes to do two different ignition maps for two different types of fuel.

Derby

To give you bettter miliage form higher octane fuel.

This woudl idicate a slight timing problem,I believe? Otherwise, the miliage would not change

Lower volume engines require higher compressiuon ratios, hence higher octane to allow ignition at the 'optimal power moment'. That is why racing engines need high octane ( max power @ high compression).

Its the reason that the lil Merlin engine gave 1,650 hp in your Grampas' Mustang on 100/130 octane, while your Grammas'
Lavochkin needed a heavier engine ( higher volumetric) to keep up...:smokin:

Best layman's explanation of Octane vrs power curve I've seen in long time!

Now, about your Gramma's Lavochlin...:wink:
http://pratt.edu/~rsilva/index.htm

The thing with the ecu is that is programmed in a room with a constant temperature and constant humidity. In normal driving conditions the ecu will retard ignition. Derby
Who told you this?

Nobody told me.
I worked at a company for a while that programmed ecu's for LPG systems. And the base maps were created in a office. And off course the ecu can interpolate the data and has a certain freedom of choosing the right timing, but that is for a reason.
What is your point of view on this matter?

What I wanna say is that the engine never runs on the limit of knocking/no knock.

Derby

Don’t know what is LPG, sorry…

I left engine R&D in the mid 90th, and at that time everything in engine design (including ECU software) were first designed and put together in the office and then checked and tested in the field, and corrected accordingly, in several iterations. In terms of base maps it means the first version was definitely created based on static dyno data, and then it was modified based on the subsequent field tests. I do not have any reason to think the procedure changed to worse since those times.

Actually, CNG, compressed natural Gas , is more likely.

LPG is used in vehicles used confined spaces due to low emissions( mines, malls, etc.)
Thx
Reg

Oh, yeah, and the second part, sorry :)
My take is that engine is tuned to run optimal ignition timing whenever possible - this is the only way to have highest possible power and highest possible efficiency simultaneously; and engine is designed so that optimal timing is pretty close to the detonation limit on full throttle – again, this is the only way to get maximum out of the given engine. Of course, recommended octane rating assumed.

@MishaA. Reaction on your first comment,
You have no reason to think the procedure has changed since then, but you give the answer yourself. Testing. Testing is expensive. And the only thing that counts these days is emission regulations. Fuel economy isn't of any interest.

LPG (liquid petrol gas) is a common fuel in europe. It can be found at most gas stations through out europe. CNG is something else, and is a lot harder to implement in vehicles.

I have reason to believe what you say but on the other side I keep wondering about exhaust gas temp. (catalyst temperatures) in combination with high CR's. And BMW definately run better on high octane fuel then on normal octane.

Someone with more info about that?

Derby

someone gave me a half a bottle of iso-octane. what can I do with it. I am interested in knowing if I can use this in my truck. like put about 4oz to a tank of 87 octane. What will that do.

like put about 4oz to a tank of 87 octane. What will that do.
Absolutley nothing. It will raise the octane rating to about 87.3, which will have no effect on anything.

Oh, yeah, and the second part, sorry :)
My take is that engine is tuned to run optimal ignition timing whenever possible - this is the only way to have highest possible power and highest possible efficiency simultaneously; and engine is designed so that optimal timing is pretty close to the detonation limit on full throttle – again, this is the only way to get maximum out of the given engine. Of course, recommended octane rating assumed.

Advancing the ignition timing to the edge of detonation does not produce best power. Altering the ignition advance under assorted condtions of throttle position, engine temperature, inlet pressure and mixture to position the combustion pressure peak at the proper crank angle is what will produce maximum performance.

Detonation is not determined by the flame front except if the flame front is slow. Detonation is the spontaneous combustion of the end gas volume prior to the arrival of the flame front. The very sudden combustion sends a high velocity shock wave across the cylinder which is measured in kilohertz. The pressure waves remove the protective boundary layer from the piston and head allowing metal to be eroded by the heat and pressure. Detonation always occurs after top dead center but very close to TDC.

I agree with most! Octane is a money making tool! Since the advent of computer control systems on vehicles in the mid 80's, there is no need for high octane fuel!!!! Only if you are HIGH PERFORMANCE IE: compression, cams, gearing and so on! But even when I was tooling around in my 56 chevy 301 small block in 1969; I just put a couple of mothballs in my 14 gallon tank!!! You can still buy them anywhere! AH! Ketones and Acetones!! Burn the house down!!!!

When I was 16 filled up my 1991 Geo Metro with 93 and put in 4 bottles of Turbo 108. The car had a hard time starting with that tank of gas.

-Mark

all right