Living in the midwest (KS), I notice a significant drop in MPG during winter. I know cold weather has a lot to do with that, but I also hear that "winter gas" is also to blame. When does summer (normal) gas typically arrive? Reason for asking: I consistently got 20 MPG in my SUV for the past 3-5 tanks. This is mostly City driving -- same types of speeds/style each day. However, I filled up this week, and got 21.7 (much closer to my "summer" mileage). Driving style/route was the same. Temp was the same. Did the winter gas already go away in KS? I typically fill at Costco.
When does "winter" gas typically go away?
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There are more than just 2 "flavors" of gasoline. It is adjusted throughout the year several times.
I think "winter" gas is falsely blamed for drops in mileage.
Used to be, at least here, that winter fuel was required to have ethanol, and summer fuel wasn't, for oxygenation/emissions purposes. In winter, if you had a fuel injected car, your mileage would go down as the injection increased the fuel delivery to compensate.
Now ethanol is used year round at almost all gas stations, and in most parts of the country there was never an ethanol requirement to begin with, so that particular cause of a change in economy doesn't really exist any longer.
There are differences in the fuel BLENDS used throughout the year and throughout the company, dictated largely by the EPA, and they mainly alter the volatility of the fuel, but not the actual energy content, so mileage should not really be affected by these different blends.
On the other hand mileage is affected in multiple ways (all bad) by cold weather, which is what everybody notices, and people tend to want to blame the fuel.
Used to be, at least here, that winter fuel was required to have ethanol, and summer fuel wasn't, for oxygenation/emissions purposes. In winter, if you had a fuel injected car, your mileage would go down as the injection increased the fuel delivery to compensate.
Now ethanol is used year round at almost all gas stations, and in most parts of the country there was never an ethanol requirement to begin with, so that particular cause of a change in economy doesn't really exist any longer.
There are differences in the fuel BLENDS used throughout the year and throughout the company, dictated largely by the EPA, and they mainly alter the volatility of the fuel, but not the actual energy content, so mileage should not really be affected by these different blends.
On the other hand mileage is affected in multiple ways (all bad) by cold weather, which is what everybody notices, and people tend to want to blame the fuel.
My parents do the snowbird thing and drive to Florida and back every winter.
They will go through a number of full tanks of fuel to make this trip. On the way down, fuel economy instantly increases at the first fill up on the southern side of the US border, even though the weather hasn't changed. It's also about 30%+ cheaper.
The next fill up, economy again instantly increases. I think he said it levels off somewhere in TN at levels than cannot be attained on Canadian fuel at any time of year.
These instant changes in fuel economy can only be attributed to the fuel - not air density, cold weather messing with fuel mixture, cold starts, sensors etc... The pattern is always north/south (worse economy the further North you go) even if one brand is used at every fill up.
They will go through a number of full tanks of fuel to make this trip. On the way down, fuel economy instantly increases at the first fill up on the southern side of the US border, even though the weather hasn't changed. It's also about 30%+ cheaper.
The next fill up, economy again instantly increases. I think he said it levels off somewhere in TN at levels than cannot be attained on Canadian fuel at any time of year.
These instant changes in fuel economy can only be attributed to the fuel - not air density, cold weather messing with fuel mixture, cold starts, sensors etc... The pattern is always north/south (worse economy the further North you go) even if one brand is used at every fill up.
When my brother visits Chicago, he always notes the cruddy gas mileage from the Northern fuels. Pretty consistent.
I have heard that winter blend gasoline has C4's (essentially Butane) added to increase vapor pressure. Not sure when production of winter blend gas ends, but I can find out when I go to work on Monday. I work in a large oil refinery here in Houston. No...I am not an Urban Cowboy. My name isn't Billy Bob or Bubba either. 
My car is also getting 1-2 MPG better this tank. I think Costco in KS got some good, "non-winter" gas last time.
http://www.fueleconomy.gov/feg/factors.shtml
Government says that typical summer gas has 1.7% more energy than winter gas. Since that's an average, I'm sure that the northern areas loose more than that, while the southern areas lose less.
Government says that typical summer gas has 1.7% more energy than winter gas. Since that's an average, I'm sure that the northern areas loose more than that, while the southern areas lose less.
Originally Posted By: Scimmia
Government says that typical summer gas has 1.7% more energy than winter gas.
Thank you for finding and posting that. To flesh it out, if you accept it then the difference is worth only 1/3mpg if you get 20mpg to begin with. Consequently mileage differences of even a single mile per gallon are due primarily to other factors.
Unfortunately, almost everything about winter driving is hard on fuel economy.
Government says that typical summer gas has 1.7% more energy than winter gas.
Thank you for finding and posting that. To flesh it out, if you accept it then the difference is worth only 1/3mpg if you get 20mpg to begin with. Consequently mileage differences of even a single mile per gallon are due primarily to other factors.
Unfortunately, almost everything about winter driving is hard on fuel economy.
Would things be overall better if we didn't have to have a hundred different blends of fuel?
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