Gas Formulas winter/summer

[Little6pack]

Does anyone know when the gas refineries change the formulas over to the winter gas? & when does it hit the pumps?

 

[Little6pack]

I may have found an answer to my own question.

Typically a refinery will start getting the winter gas refined 30 days in advance for sale after labor day

Technically, the EPA allows companies to start selling gas with a Reid vapor pressure rating of 9.

The Reid vapor pressure of gasoline is a measure of the amount of volatile organic compounds, or VOCs, that will be released when the fuel is burned.

Summer-blended formulated gas has a Reid vapor pressure of between 7 and 8. The allowable Reid vapor pressure increases through the winter, EPA officials said, starting with 9 in September and rising to 11 to 13 later in the winter. The maximum allowable under any circumstances is 15

 

[bruce]

Typically the second week of Oct and 2nd week of Apr. That can vary by refinery and typical temps..

 

[TylerDurden]

after reading your reid vapor info, what does that mean, summer or winter gas is better??????

 

[bruce]

Originally posted by TylerDurden
after reading your reid vapor info, what does that mean, summer or winter gas is better??????

There are a number of items that go into blending fuel. The quality of the additive package is what makes a particular gas good. Up until the local distributor it all comes out of the same pipeline.

Basically, winter gas evaporates quickly in summer temps, and summer fuel is more difficult to start a car with in winter months.

 

[ijames]

Reid vapor pressure doesn't measure properties after burning, it measures how readily the liquid gasoline will evaporate. The higher the vapor pressure the faster/easier it will evaporate. Since gasoline is a witch's brew of lots of different components, the mix doesn't have a single, simple vapor pressure like a pure compound (like water) does, so they use the Reid vapor pressure which gives an average value for the mix. In winter you need a higher vapor pressure fuel to get cold engines started, but in summer that high a vapor pressure would lead to lots of losses by evaporation from storage tanks (producing VOC hydrocarbon pollution). The refineries keep the octane rating the same, so winter gas is not really any better or worse than summer gas, it just works better in the season its designed for.

 

[SinistrV6]

Butane is the biggest difference...

It's true that gasoline is a "witch's brew" of components (varies from 9 to 13 depending on time of year and octane). The amount of butane is the primary difference in Winter, Summer, Intermediate and Transition grades of gasoline. Refiners would much rather sell a barrel of butane as a barrel of gasoline whenever possible!

 

[ijames]

Richard, I guess it depends on how you define component. I meant chemically distinct molecular structures, so each isomer gets counted, and there are more like 300-500 components in gasoline. Sorry for the confusion.

 

[Lee_Burough]

Not to hyjack your thread, but, I've been wondering about Zylene and how it might interact in my gas tank over the winter.

Will its increase in octane still be there in a couple months?

 

[ijames]

Yes, the xylene will still be there. Normal gasoline contains some toluene and xylene anyway, and it is very stable chemically so will store just fine.

 

[2quiktocare]

I think the only thing they reformulate in California is there pricing structure.

 

[Little6pack]

Originally posted by lburou
Not to hyjack your thread, but, I've been wondering about Zylene and how it might interact in my gas tank over the winter.

Will its increase in octane still be there in a couple months?

Good question.. I don't know about Zylene..

BUT I put a full tank of 94 in my GN.. 6 month later the octaine was gone.. Mildly stepping on the gas would bring the knock levels up on my first few drives.. Had to drive like a granny for the fuel to go away..

This year I am keeping 1/2 tank full.
I will drive next spring to the Sunoco & buy 4 to 5 gallons of CAM2 100 oct to REBOOST the level