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Discussion Starter · #1 ·
I keep seeing people talk about winter gas and it being part of the issue with bad MPG in the winter. What is the difference in winter gas from any other time of the year? why does it cause worse fuel economy??
 

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Summer blends contain 2% butane, and winter blends contain 10% butane. Part of this is to raise or lower the RVP value of gasoline. Summer blends have a lower RVP (Reid vapor pressure) to prevent gasoline from flash boiling or vaporizing too quickly in open containers in high summer temps.
That's the reason for altering the blends from summer to winter.
Now if you look at the BTU values of Butane and Gasoline. Butane has a lower BTU value, so you will have to burn more of it to get the same output of Gasoline. Thus adding more butane to gasoline will have a negative effect on it's energy output. So you will need more winter fuel to get the same output as summer fuel.
 

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Discussion Starter · #5 ·
Summer blends contain 2% butane, and winter blends contain 10% butane. Part of this is to raise or lower the RVP value of gasoline. Summer blends have a lower RVP (Reid vapor pressure) to prevent gasoline from flash boiling or vaporizing too quickly in open containers in high summer temps.
That's the reason for altering the blends from summer to winter.
Now if you look at the BTU values of Butane and Gasoline. Butane has a lower BTU value, so you will have to burn more of it to get the same output of Gasoline. Thus adding more butane to gasoline will have a negative effect on it's energy output. So you will need more winter fuel to get the same output as summer fuel.
great post Stump3r! I am at 9mpg city right now with a pretty light foot... I figure (based on what the overhead console says) I have lost 3-3.5 mpg easily since the colder temps started. I guess it would vary by area but do you know when they start changing the blend?
 

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great post Stump3r! I am at 9mpg city right now with a pretty light foot... I figure (based on what the overhead console says) I have lost 3-3.5 mpg easily since the colder temps started. I guess it would vary by area but do you know when they start changing the blend?
According to what I've been told the switch starts to happen around September then back to summer fuels come March. That is refinery side. So by the time it hits retailers would be October / April. That's pretty much the window that I see my fuel economy tanking!
 

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Discussion Starter · #7 ·
According to what I've been told the switch starts to happen around September then back to summer fuels come March. That is refinery side. So by the time it hits retailers would be October / April. That's pretty much the window that I see my fuel economy tanking!
ya that is about when I figure my fuel economy started getting worse.... Thanks for the info Stump3r
 

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