Summer grade gas

Has anyone noticed whether summer grade is here yet? Because in Southern Ohio we are still using winter grade. I am just curious to know b/c isn't the price supposed to go up some when we hit summer?

I don't think that the winter grade has left us here in Maryland, but they are now selling our gas where I live with 10% ethanol mixed in.
I have noticed a drop in mileage with the mixed gas - about 17 MPG vs 19-20 normally.

It should be there within the next two weeks.

Go to a station with a lot of traffic so the tanks will be refilled constantly.

ethonal is a great filler for the statioins to use, it burns at a rate of 7:1 instead of 14:1 like gas, so they pump it with etho, which is half the price as gas, and get you to buy more because you go through more

Has anyone noticed whether summer grade is here yet? Because in Southern Ohio we are still using winter grade. I am just curious to know b/c isn't the price supposed to go up some when we hit summer?

Not sure on the summer mix but.
10-4 on the price is going up.:grinyes: :lol:
MT

HELLO;
well our gas is dropping, its down to $2.62 in Celina,Ohio. It was $2.89 on monday

Do they switch the gas down in Southern FL also or just leave it the same year round (because we don't really have a winter)

Yes, I believe all do.

I don't think that the winter grade has left us here in Maryland, but they are now selling our gas where I live with 10% ethanol mixed in.
I have noticed a drop in mileage with the mixed gas - about 17 MPG vs 19-20 normally.
i think it has. i've noticed an increase in mileage in my 95. also tried an acetone cycle and went up another mpg or so (tried it with winter gas and acetone had no effect). price went down for gas a few cents but i think its all a tease and will shoot up again.

Alcohol which is the realative difference between summer and winter gas completely counteracts the benefits of the acetone.

Summer gas is the only time of year to use it to lower combustion temperatures, reduce ping and advance the computer controlled timing.

Alcohol which is the realative difference between summer and winter gas completely counteracts the benefits of the acetone.

Summer gas is the only time of year to use it to lower combustion temperatures, reduce ping and advance the computer controlled timing.
thats why i stopped using it during the winter and just now started using it again

ethonal is a great filler for the statioins to use, it burns at a rate of 7:1 instead of 14:1 like gas, so they pump it with etho, which is half the price as gas, and get you to buy more because you go through more
BASTARDS!!! Isn't that illegal??

BASTARDS!!! Isn't that illegal??
no, they make the rules :lol2:

etho, which is half the price as gas, and get you to buy more because you go through more
this is why u don't use E-85. this says it all;
http://www.fueleconomy.gov/feg/byfueltype.htm

nope, not illegal because alcohal displaces the water that you would get in the winter time and like zl1 said, that is why you dont wanna use e 85... unless youve not hugged a tree in a loong time

Edit- I am retarded, sorry

NE Ohio has been on summer blend since beginning of May.

What does summer gas mean?

NE Ohio has been on summer blend since beginning of May.

What does summer gas mean?

Less Alcohol and therefore better mileage and power.

I wanna say in MA they must have switched within the last week because I am getting better mileage and more power. One funny thing though is the other day I put over 18 gallons in my tank which I did not think was possible. I thought I had an 18 gallon tank and the most I had ever dumped in before was maybe a little under 17. Very odd.

I wanna say in MA they must have switched within the last week because I am getting better mileage and more power. One funny thing though is the other day I put over 18 gallons in my tank which I did not think was possible. I thought I had an 18 gallon tank and the most I had ever dumped in before was maybe a little under 17. Very odd.
i think 4 drs have 19 gallon tanks and 2 doors have 20 gallon tanks.

I thought it was 18 for me? Maybe not

Summer grade gas has nothing to do with alcohol, It has to do with vapor pressure. Butane is added to increase the pressure (in winter) usually and not many can ever tell.

Summer grade gas has nothing to do with alcohol, It has to do with vapor pressure. Butane is added to increase the pressure (in winter) usually and not many can ever tell.

Yes, it is the alcohol level that is increased.

Butane? Isn't that a gas?

Butane is a liquid (under pressure) and a gas at ambiant temp and pressure, like propane only the vapor pressure is less.

I suppose a distinction should be made about the two alcohols and also many different brands will change for various reasons.

Methanol is added in winter for fuel line anti-freeze. It way under 1% and will never be noticed for mpg or hp sake.

Ethanol is added at (up to) 10% and is used all year round, but may not be used from time to time, but not haveing anything to do with winter/summer. When ethanol blend fuel is used the methanol is not added even in winter.

I hear some people claiming lower mileage with ethanol, but I would be hard pressed to be able to tell you the difference if you filled my tank and made me guess which fuel you had used. I think I'd have better luck smelling it than one or two tanks of mpg tests. Theoretically the ethanol blend should have a few % lower mpg and 85% ethanol is claimed to get 10% less mpg. This I do believe,,,,

The truth is that over 99% of people probably have no idea what gas they're using and even if they do know, it doesn't make any difference anyways.

Butane is a liquid (under pressure) and a gas at ambiant temp and pressure, like propane only the vapor pressure is less.

I suppose a distinction should be made about the two alcohols and also many different brands will change for various reasons.

Methanol is added in winter for fuel line anti-freeze. It way under 1% and will never be noticed for mpg or hp sake.

Ethanol is added at (up to) 10% and is used all year round, but may not be used from time to time, but not haveing anything to do with winter/summer. When ethanol blend fuel is used the methanol is not added even in winter.

I hear some people claiming lower mileage with ethanol, but I would be hard pressed to be able to tell you the difference if you filled my tank and made me guess which fuel you had used. I think I'd have better luck smelling it than one or two tanks of mpg tests. Theoretically the ethanol blend should have a few % lower mpg and 85% ethanol is claimed to get 10% less mpg. This I do believe,,,,

The truth is that over 99% of people probably have no idea what gas they're using and even if they do know, it doesn't make any difference anyways.

If butane is only a liquid under pressure, than why are you saying it is the difference when you put in a non pressurized gas tank and it turns into a gas?

There is a difference in performance noted by several drivers and this is no fairy tale like you are making it out to be.

The heating value also varies by grade and by season. On average, the heating value of premium-grade gasoline is about 0.7 percent higher than regular-grade because premium-grade, in general, contains more aromatic hydrocarbons — the class of hydrocarbons with the highest densities. The heating value of winter gasoline is about 1.5 percent lower than summer gasoline because winter gasoline contains more volatile, less dense hydrocarbons.

Oxygenated gasolines, which are required in some areas of the U.S, have lower heating values because the heating values of the oxygenate components are lower than those of the hydrocarbons they displace. The percentage decrease in heating value is close to the mass percent oxygen in the gasoline. For example, gasoline in carbon monoxide nonattainment areas must be oxygenated to a minimum of 2.7 mass % oxygen during four or five winter months.6
Footnotes

6 Nonattainment area is an EPA designation for an area where an air pollutant, carbon monoxide in this case, exceeds the limit established by the National Ambient Air Quality Standards more often than allowed.
As a result, its heating value is about 2.7 percent lower than conventional gasoline. Federal reformulated gasoline and California Phase 3 reformulated gasoline in federal reformulated gasoline areas must be oxygenated year-round to an average oxygen content of about 2 mass %. As a result, their heating values are about 2 percent lower than that of conventional gasoline. In addition, California Phase 3 reformulated gasoline sets some limits on distillation temperatures and aromatics content, which have the secondary effect of lowering the density of the fuel compared to conventional gasoline. This reduces the heating value by about another 1 percent.

http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/1_driving-performance/pg4.asp

Ethanol has not been the oxygenate of choice for summer RFGs because the volatility increase makes it more difficult to meet the very tight vapor pressure limits of these gasolines. Now, with many RFG areas banning MTBE, more volatile hydrocarbons will have to be removed at the refinery to make RBOB.

http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/4_oxygenated-gasoline/pg2.asp#performance_issues

Oxygenates are fuel additives (alcohols and ethers) that contain oxygen which can boost gasoline's octane quality, enhance combustion, and reduce exhaust emissions. The term oxygenated gasoline most commonly refers to the wintertime program that reduces emissions of carbon monoxide (CO) from motor vehicles. Although required by the federal Clean Air Act, winter oxygenated gasoline programs are implemented by the states. This section provides information about oxygenated gasoline, winter oxygenated gasoline areas, oxygenates (such as ethanol and MTBE), and health effects testing of oxygenates.

http://www.epa.gov/otaq/oxygenate.htm

Affects on fuel economy

http://www.epa.gov/otaq/regs/fuels/ostp-3.pdf

Oxygenated Gasolines and Fuel Economy

http://www.chevron.com/products/prodserv/fuels/bulletin/oxy-fuel/

Oxygenated Gasoline

Chemistry
Oxygenated gasoline is a mixture of conventional hydrocarbon-based gasoline and one or more oxygenates. Oxygenates are combustible liquids made up of carbon, hydrogen, and oxygen. All the current oxygenates belong to one of two classes of organic molecules: alcohols and ethers.1
Footnotes

1 The word ether reminds many people of the anesthetic. Although the anesthetic commonly is called ether, its correct chemical name is diethyl ether (CH3CH2OCH2CH3). It is not used as a gasoline oxygenate because it is too volatile.
In alcohols, a hydrocarbon group and a hydrogen atom are bonded to an oxygen atom: R-O-H, where "R" represents the hydrocarbon group. All alcohols contain the "OH" atom pair. In ethers, two hydrocarbon groups are bonded to an oxygen atom; the groups may be the same or different: R-O-R or R-O-R'.

This is from Chevron themselves stating that they use alcohol as an oxygenate in the winter months which has less heat per unit and therefore more of it has to be used for the same power unit production.

If you want to argue with the gas manufacturers and the government, go right ahead. Butane is a gas at our operating temperatures and therefore has no bearing seeing it will evaporate out of the fuel during production, transportation and filling our tanks.

That is if it is even a constituent.

F.Y.I. National winter/summer change in fuel is June 1st across the board. Also as of 2007 I believe the oil companies will stop using methanol in the fuel mixture due to emissions. a little info I came across earlier this week I thought you all might want to know

We should also make a distinction between reformulated gasoline (which we are not using here in Ohio) and the summer/winter blend. The diifference in summer /winter is the vpp and has nothing to do with oxegenated or reformulated gas, it has nothing to do with the additives, ethanol blend, methanol or that long additive word that shell uses. It is a vapor pressure issue , and quite frankly has nothing to do with using the gas in a vented or open tank.

As for your one question about the butane which is added to increase vapor pressure (add to summer gas for the winter) The butane really is a liquid under pressure (not only that) it is also a vapor above that liquid space and a vapor in an open container. If the temp is cold enough then we can simply carry it around in an open bucket just like water and is colorless and may even be odorless. The only way to get the vapor is to heat it abov the boiling point (like water) and the only way to get a pressure is to cap it up like plugging up a boiling pot of water on a stove.

Adding Butane to gas does have a ratio of escape, it is very little. The butane stays mixed and increases vapor pressure of the fininshed product.

It is not a fairy-tale per say, but the consumer does not have to know and cannot tell. As far as the fairy tale you have accused me of making out. I can say this that a performance difference between a full and empty tank of fuel would be far more noticeable by a driver than nearly any difference in gas blend from time to time or station to station or brand to brand.

Just to be clear, we are not talking about octane, e-85,reformulated gas, ect. Only summer / winter blends, I really do not know any more about gasoline, I know a bit more about butane and far more about propane (both LP gas)

We should also make a distinction between reformulated gasoline (which we are not using here in Ohio) and the summer/winter blend. The diifference in summer /winter is the vpp and has nothing to do with oxegenated or reformulated gas, it has nothing to do with the additives, ethanol blend, methanol or that long additive word that shell uses. It is a vapor pressure issue , and quite frankly has nothing to do with using the gas in a vented or open tank.

Throughout all the reading I have done about winter gas and the differences, not one fuel company has named butane as a constituent in winter gas.

Winter gas is oxygenated gas and what they use to oxygenate the gas is alcohol, not butane, alcohol.

As for your one question about the butane which is added to increase vapor pressure (add to summer gas for the winter) The butane really is a liquid under pressure (not only that) it is also a vapor above that liquid space and a vapor in an open container. If the temp is cold enough then we can simply carry it around in an open bucket just like water and is colorless and may even be odorless. The only way to get the vapor is to heat it abov the boiling point (like water) and the only way to get a pressure is to cap it up like plugging up a boiling pot of water on a stove.

I still don't get where you think butane, which is a gas under normal pressures seen in a gas tank is what makes the difference in the winter fuel.

Read the links, see the information from the government and the fuel companies and you will see that the difference is alcohol, not butane, alcohol which has a lower amout of heat per unit volume and thus we use more of it to create the same unit of power.

Adding Butane to gas does have a ratio of escape, it is very little. The butane stays mixed and increases vapor pressure of the fininshed product.

I am sorry, but a gas does not stay mixed in the fuel. It will easy escape. We are not talking about a thick fluid here to trap the gas vapor.

It is not a fairy-tale per say, but the consumer does not have to know and cannot tell. As far as the fairy tale you have accused me of making out. I can say this that a performance difference between a full and empty tank of fuel would be far more noticeable by a driver than nearly any difference in gas blend from time to time or station to station or brand to brand.

What?.... They sure as hell know that the winter fuel is crap. More fuel consumption, less power and you don't think they know. They all more or less know that the summer fuel is better.

Just to be clear, we are not talking about octane, e-85,reformulated gas, ect. Only summer / winter blends, I really do not know any more about gasoline, I know a bit more about butane and far more about propane (both LP gas)

Summer grade gas has nothing to do with alcohol, It has to do with vapor pressure. Butane is added to increase the pressure (in winter) usually and not many can ever tell.

Earlier you said that alcohol had nothing to do with the difference between summer and winter gas blends and you are stating that it has nothing to do with alcohol which is flat out wrong. There is no room for debate, alcohol concentration is the key difference and the proof is there in the links provided.

No, your links prove otherwise and say that although it used to be that way it is not any more, your links also reference 3 or 4 different reformulated gasolines and Ca as the state. I am responding to original post in s. Ohio. We may have just a few Chevron stations here.

On the "alcohol" please make a distinction as to which alcohol you are refereing to because it is true that "methanol" is added in non-ethanol blended fuels in the winter for fuel line freeze protection, but does not change the vpp of the gas as the quantity is very minute. Some have not had methanol for 10 years or so.


It seems in addition to making a mountain out of a mole-hill as your own chevron links provide a 3% max difference in mpg test , they also agree with what I say when they say that the average driver will not see a differenence. If you'd like to get lost in the details, then specific time periods and specific stations need to be named as it can vary from station to station as to the alcohol content.

Being specific in my NE Ohio area clecev and akron and canton and toledo and columus. Marothon bp, citgo (as of less than 1 year) are using 10% alcohol (ethanol) along with many others. Shel will soon use it also and lots of the generic stations do not use ethanol and may or may not use methanol.

This info is time sensative and I think soon we will be on 20 % ethanol blend.

On the Butane, some makers do it at the refinery to change the pressure of the gas and some "generic" places will push the butane right into the storage tank of "summer" gas

I'll be the first to admit that I'm not an expert on winter formulations, but I found an article that may help this discussion a little. I also want to compliment you guys for keeping the discussion civil.

http://zhome.com/ZCMnL/PICS/winterGas/winterGas.html

THE TRUTH ABOUT WINTER GAS.

BY JOHN HUNKINS

As l write this, a suffocating blanket of snow clouds looms on the horizon while thousands of tanker trucks with winter gas roll inexorably toward gas stations in the Northeast and Midwest. In spite of the fact that I'm not a meteorologist, I know exactly what the clouds and cold weather will bring. Yet though I am an automotive journalist, I don't have the foggiest idea of what chemical grog fills those shiny stainless-steel tanks. It's surely got to be bad, no?
And as winter's pall approaches New Jersey once again, the CSK office grumblings about winter gas resurface. While joining the ritual chorus of nay-sayers, I found myself thinking, What the hell do I really know about winter gas? Or for that matter, what do I know about fuel? Nothing.
Funny how we're all experts on making horsepower, but nobody knows anything about fuel other than pour magic juice in, engine go boom-boom. Considering that horsepower comes from the fuel and not the high-dollar parts, wouldn't you say there's a pretty big gap in the information super highway? The realisation made me feel awkward, like a heart surgeon who doesn't know basic first aid.
To satisfy my curiosity about fuel in general and winter gas in particular, I put in a call to Thomas Hart, a fuel chemist with a master's degree from Georgia State University. He's designed many spec fuels for racing, including Formula One, NASCAR, NHRA Pro Stock and motorcycles, and has previously owned his own race fuel company, Turbo Racing Gasoline.
Thomas explained that gasoline is made up of many different chemicals, or components, not just one uniform molecule. Smaller, lighter components have a high volatility (they evaporate easily) and boil at a lower temperature, whereas heavier, more complex components don't evaporate as easily and boil at a higher temperature.
Each fuel has its own unique signature, called a distillation curve; think of it as a recipe. The distillation curve tells the chemist which components are in the fuel and what their weights (e.g., their boiling points) and quantities are in relation to each other. A simplistic way of looking at the distillation curve would be to list all the fuel's components on a sheet of paper with the heaviest ones at the bottom and the lightest ones on the top.
The trick is to have the right fuel for the right time of year. In the summer, when the temperature is high, the presence of too many light components will cause the fuel to evaporate too readily. This can result in vapour lock, an over-rich mixture and excessive evaporative emissions. In the winter, too many heavy components keep the fuel from evaporating, causing hard starting, a lean mixture, heavy hydrocarbon emissions and poor converter light-off.
Obviously, since we can't change the weather, we have to use a fuel that will optimize performance and emissions for a particular climate. To do this, fuel manufacturers use heavier components in the summer and lighter components in the winter. This is a simplification of things, but it's close enough for government work.
For reformulated winter gas, lighter, low-boiling-point components are added to the gasoline to increase volatility. This makes your car easier to start and accelerates converter light-off, thus lowering emissions. That's the official line on reformulated gas.
And now for the teaser. According to Thomas, one of the most popular compounds gasoline refiners used to pump up the brew is called methyl tertiary butyl ether (MTBE).
"'MTBE has several good things about it" says Thomas. "One, it boils in a range where the components have a fairly poor octane value. MTBE enhances the octane in the distillation curve. It fills in a good hole there around normal hexane and normal heptane. MTBE has an extremely high octane number, over 108. You've normally got some real junk [in the distillation curve]. [MTBE also] helps on acceleration and cold starting. On a carbureted car, it helps on fuel distribution." Gearhead translation: MTBE is a big check in the horsepower column.
With a little fuel chemistry under my belt, I called Mitch Markusich, the proprietor and head brewmaster of PRO Racing Fuels in Mississauga, Ont., Canada.
"The essential difference between summer fuels and winter fuels is the vapor pressure," says Mitch. "Manufacturers do this by pumping up the mixture with light-end components like butane, propane and isobutane." The caveat, according to Mark is that these components all have high octane values as well.
Shoring up the positive aspects of additives like MTBE, which Thomas earlier asserted, Mark said, "Another major property in [reformulated winter gasoline] is the use of oxygen-bearing ether compounds like MTBE, ETBE (ethyl tertiary butyl ether) and ethanol. It's like pouring liquid oxygen into the combustion chamber. The engine doesn't have to draw the oxygen in because it's already available in the fuel."
To illustrate his point, Mark pointed out that in Canada, where his racing fuels are made and used, the government doesn't allow the use of lead in racing fuels. Instead, PRO uses (among other components) MTBE to increase the oxygen content and octane of its fuels. Mark also pointed out that oxygen-bearing compounds like propylene oxide (a fuel additive outlawed in many racing organizations) and nitromethane have a considerable amount of oxygen in their makeup, over 5O percent in the case of nitromethane (By comparison, a 14-15 percent constitution of MTBE would give pump gas around a 2 8 percent oxygen content.)
So what does all this mean? Obviously winter gas can't be compared to race fuel; the recipes are too dissimilar. Pump gas must adhere to ASTM specification D4814, which puts specific limits on the composition of highway fuel. But within these limits, there is some blending flexibility. And in many Northern states, there is also the requirement for reformulated fuels.
Here's the poop: As specified by state law, reformulated winter gas contains any number of lighter, lower-boiling-point hydrocarbons (butane, propane, etc.) that just so happen to have an excellent octane value. Added to this may be any number of oxygen-bearing ether compounds (MTBE, ETBE, ethanol) that improve emissions and also have a relatively high octane blending value.
So what's all the bad hype for? Price, for one thing "It's actually more expensive to make reformulated winter gas than normal, summer fuel, ' says Thomas Hart. Lower fuel economy is another concern.
"The oxygen-bearing compounds displace fuel components, so it takes more fuel to get the job done. Normal gasoline has a stoichiometric ratio of 14.7:1, reformulated winter fuel runs between 14.3 and 14.4:1," says Mitch Markusich.
And the complaints about poor performance? Mitch says, "When people bitch about the fuel, it's not really the fuel's fault. The weather is largely responsible; after all, it is winter. Low cranking voltage in the battery, increased oil viscosity, atmospheric condensation in underground fuel tanks and so forth."
The bottom line is that when it's cold, winter gas seems to be the hot ticket for performance enthusiasts. Not only is the dense winter air good for horsepower, but the higher oxygen content and octane value of winter gas make the pot sweeter And as for fuel economy and price? When did that ever get in the way of having a good time behind the wheel? It s just too bad we have to deal with all that snow and ice".

This is an interesting discussion. I had seen reference in previous posts in other topics that stated that ethanol content was the only (or major) difference between winter and summer gas. I don't know the normal content of ethanol in winter and summer gas (which probably depends on where you live), so I never bothered to add to that discussion. Now that butane and pentane etc have entered the discussion, this is something I am more familiar with.

Adding ethanol to gasoline doesn't affect the vapor pressure of the gasoline very much, but adding butane, propane, iso-butane does. Ethanol may make the gas more oxygen rich and absorb some water that's in the gas line (important for winter), and in the process make us use less petroleum, but it doesn't help in making you car start easier in the winter (see the graph below and BlazerLT's reference). Adding methanol to gasoline is a bad idea. If there is any water present, methanol and the water will form a two-phase system and that is bad. The mixture is corrosive and probably not burnable.

As long as fuel distribution (evaporation and mixing) is temperature-dependent as it is, the gas in winter has to be more volatile than the summer gas. I know for a fact that the information in Blazee's reference is right on the money (as is BlazerLT's references on the composition of oxygenated fuels).

To make the gasoline more volatile and make it useful as a fuel in the winter, they introduce a greater amount of high vapor pressure components (butane, propane, and iso-butane, and pentane can be increased in the distillation process) during cold weather. The butane, propane iso-butane mixture is a commercially-available propellant that they just pressurize the holding tanks with to increase the content of these components in the gasoline. They use the same mixture in shaving cream and other propelled foodstuff (light a flame by shaving cream or deoderant spray and see what I mean).

The reason the butane/iso-butane doesn't evaporate from the gasoline (even though they are gases at above around 0 degrees F) is because the are not in the gas in very high concentration and they are in a closed system with the gas cap keeping the system closed, keeping the system pressurized. As someone said above, their propensity to evaporate is dependent on the temperature, each component's individual vapor pressure above the gasoline they are a liquid in, and their concentration in the gasoline. The vapor pressures of the components in the gas phase above your liquid gasoline are kept high enough to prevent fast evaporation by sealing the tank with the gas cap.

You will notice that there is alot of gas escaping when you remove your gas cap at certain times (hot tank from the road, warmer than normal weather, etc). This is the pressure escaping caused by the presence of the low-boiling components (butane etc). The components stay in the gas because they are hydrocarbons, just like the normal gasoline components iso-octane, octane, heptane, etc. Butane, propane, pentane, iso-butane are very soluble in the gas and remain dissolved in the gas as long as you keep the gas cap on the tank. If you have a bad gas cap that doesn't seal, the low boiling (highly volatile) components will come out of the gas and evaporate, just like gas escaping from an open bottle of soda pop or beer, just not as fast. This is not only a problem with keeping the composition of your gas as you bought it, it is an environmental problem because hydrocarbons are pollutants.

The lack of volatile components is what makes your gas go bad and unable to run your car if you let it sit with gas in the tank for 6 months or so without replenishing the gas to make it volatile again for fuel distribution purposes. That is the sign that the volatile components in the gas have escaped from the gas tank through the gasket on the gas tank cap, your hoses, your injectors, in fact everything that is not good metal tubing or a metal-to-metal seal like a swage-lock fitting (nothing rubber or plastic is a perfect seal). That's why you have to drain the gas and give the car (or lawnmower) new gas after it sits all winter.

Another effect that preferentially depletes gasoline of volatile components is diffusion through seals. Propane and butane, being smaller molecules than octane (for example), will preferentially leak through seals and be lost faster through the seals, accentuating the loss of the most volatile components.

Here is a graph from the Chevron reference posted by BlazerLT:

http://i16.photobucket.com/albums/b8/rogersb/DistillationCurve.gif

Note that if you compare summer conventional (non-ethanol) gas and winter conventional gas, that at the same amount of gas evaporated (at any fixed point on the bottom horizontal axis), the temperature of the summer gas has to be higher (vertical axis) than that of the winter gas to have evaporated the same amount in both cases. This shows how much more volatile the winter conventional gas is than the summer conventional gas, due to the higher content of butane, propane, iso-butane, etc in the winter gas. These components all boil off at a lower temperature than the other octane-weight gas components.

Notice also that in the vapor pressure measurements in the Legend at the bottom of the graph, if you compare the summer conventional and the summer reformulated with ethanol gasolines, the addition of ethanol to summer conventional gas actually lowers the vapor pressure of the gas, making it less suitable for winter use. Winter gas has to be more volatile to make up for the colder temperatures which lowers the vapor pressure of the gas. The winter conventional gas has almost twice the vapor pressure of the two summer blends - again, from the addition of high vapor pressure components, butane etc. The higher vapor pressure of the winter gas makes it evaporate and mix with the air similarly when it is cold as the summer gas does when the summer gas is hot.

butain as it is canno't be in gasolien, what happens to all the liqued in the bic lighter that gets a crack in it, it evaporates, it doesn't get the outside or the ground wet, its just gone...

Read my discussion just above yours

Ok, two neat articles. I think I can go along with most of that. Something I'm not sure I can go along with is that the butane will escape if the tank is vented.

I'm not sure, but I think that the butane will evaporate at the same rate as the gasoline. In otherwords if we set the butane enhanced gas (winter gas) out in the summer time in an open pan and a week later we had 50 % of our product left I think that the butane would still be present and the vapor pressure would still be equal when we capped it back up, right?

It will be an interesting test and if the butane comes out then concievably my "winter" gas in my vented tank would become summer gas ? after how long?

In any system that is a mixture of components, the most volatile component will escape first given the oportunity to evaporate. The components act totally independently as if none of the other components existed. Near equilibrium between the liquid and gas phases, the ratio of the rate of evaporation will be the ratio of the mole fractions of the components and proportional to their vapor pressures as pure compounds. What makes butane preferentially come out of gasoline, even though it is not in very high concentrations, is its vapor pressure as a pure liquid at room temperature is probably 100 times that of octane.

The butane will not totally evaporate and leave all the other components, but will preferentially evaporate in a ratio to the other components as I just described.

To directly answer your question, the rate of butane loss relative to the rate of loss of the other components will depend totally on how much butane is in the gas to begin with.

The answer to how long the gas will take to deplete itself of butane, is never. How long will it take to become summer gas? That will depend on the composition of the summer gas. The butane will never totally leave unless all the gas evaporates. As the butane preferentially evaporates, its rate of loss relative to the other components will slow and at some point, the loss of butane will equal that of the next most volatile component.

Don't forget, this is a reversible system. Just as the butane mixture was injected into the gasoline forcibly, the butane will escape from the gasoline just as forcibly.

Think of this system just like a distillation. In a careful distillation, you can totally get rid of the butane first, followed by all the next most volatile component, etc. If you evaporated it in a pan, you are using a bad analogy since the pan is not very reversible - the requirement for the above separation. However, the gasoline in your (pretty much sealed) tank will only very slowly loose volatile components and is much closer to a reversible system.

That's very interesting, you have explained it well, thanks.

You're welcome.

Here's an article on "What is Gasoline?

http://pubs.acs.org/cen/whatstuff/stuff/8308gasoline.html";

Here's an interesting excerpt:

"Several refinery processes follow the distillation to produce the blending components used to make gasoline. Some of the heavier fractions undergo fluid catalytic cracking to break down larger compounds into smaller compounds, usually branched alkanes. Hydrocracking is a slightly different process that adds hydrogen to unsaturated hydrocarbons as it cracks them. Catalytic desulfurization and denitrogenation use hydrogen to strip out sulfur and nitrogen, usually from aromatic compounds.

Other reactions, typically carried out on the naphtha fraction, include dehydrogenations, dealkylations, cyclizations, and isomerizations. When performed in series, these reactions are collectively known as reforming, and the product, called reformate, is rich in aromatics and branched alkanes.

Alkylation, the opposite of cracking, is a catalytic process that adds an alkane to an olefin, such as isobutane to propylene or butene. The product, called alkylate, is mostly a mix of trimethylpentanes and dimethylhexanes. Polymerization reactions also are used to join propenes and butenes to form pentanes and hexanes.

Gasoline in the U.S. is usually blended from straight run gasoline, reformate, alkylate, and some butane. The approximate composition is 15% C4–C8 straight-chain alkanes, 25 to 40% C4–C10 branched alkanes, 10% cycloalkanes, less than 25% aromatics (benzene less than 1.0%), and 10% straight-chain and cyclic alkenes.

Two important measures for gasoline are the Reid vapor pressure and the octane number. Gasoline has to be volatile enough to vaporize and mix with air to burn, but one problem is that the vapor pressure can go up or down with a change in temperature or with altitude. If the vapor pressure is too high, a vapor lock can occur and prevent the flow of gasoline; if it's too low, the engine might not perform well in cold weather. One way to control vapor pressure is by adding more or less butane."

Pretty good. That Reid vapor pressure (rvp) which I mistakenly called vpp is the difference in the summer / winter gas. The main difference is the butane content because that is the product that changes the pressure.

The strange thing is that a high (it's really not very much) Butane content will not affect mpg, I think it has more to do with winter driving conditions and habits. Myself is a good example of one who uses a lot of summer gas in the winter and vise versa. I may notice a slight mpg change related to the outside temp, road conditions, ect. , but will not notice any difference in the gas itself.

I wind up storing some gas and using it in the wrong season , hehe. Her'es a funny story that happened to me about 20 years ago.

We had a number of snowmobiles and got tired of going to store, buying gas and using cans and such. We decided to use a 55 gallon drum and would take it to the station to get it filled. We were having difficulty getting the gas to come out fast enough so we used a 20 # lp tank with a 2-3 # regulator and pressured the drum slightly.

Well soon enough someone forgot to turn off the lp tank and the first few times it was empty it went unnoticed and merely got refilled thinking the lp just leaked out the top of the drum of gas. This went on just a few times when all of the sleds started vapor locking constantly just like pionted out in the above link. It took us a while to figure out what was happenning. The lp gas was going into the gasoline and causing the vapor press. to increase. When used in the engine compartment where it was a bit warm would cause bubles to form in the lines and such.

Pretty dumb move anyways,, the lp went into the gasoline from the top (the vapor space) which is kinda surprising to me.

Pretty good. That Reid vapor pressure (rvp) which I mistakenly called vpp is the difference in the summer / winter gas. The main difference is the butane content because that is the product that changes the pressure.

The strange thing is that a high (it's really not very much) Butane content will not affect mpg, I think it has more to do with winter driving conditions and habits. Myself is a good example of one who uses a lot of summer gas in the winter and vise versa. I may notice a slight mpg change related to the outside temp, road conditions, ect. , but will not notice any difference in the gas itself.

I wind up storing some gas and using it in the wrong season , hehe. Her'es a funny story that happened to me about 20 years ago.

We had a number of snowmobiles and got tired of going to store, buying gas and using cans and such. We decided to use a 55 gallon drum and would take it to the station to get it filled. We were having difficulty getting the gas to come out fast enough so we used a 20 # lp tank with a 2-3 # regulator and pressured the drum slightly.

Well soon enough someone forgot to turn off the lp tank and the first few times it was empty it went unnoticed and merely got refilled thinking the lp just leaked out the top of the drum of gas. This went on just a few times when all of the sleds started vapor locking constantly just like pionted out in the above link. It took us a while to figure out what was happenning. The lp gas was going into the gasoline and causing the vapor press. to increase. When used in the engine compartment where it was a bit warm would cause bubles to form in the lines and such.

Pretty dumb move anyways,, the lp went into the gasoline from the top (the vapor space) which is kinda surprising to me.

Very interesting and good info 534BC
That LP tank on the drum also explains how they can get the Butane/Propane in the gas. I sure did not know they would mix.
Years back we used Propane in farm tractors.
It was good stuff but. kinda touchie stuff filling up the fuel tanks.
Turned to liquid in the tank with the vapor on top.
The stuff would freeze you then burn you if any leaked out on the fill up.
MT