I haven't actually did any numbers but I do know that my MPG with winter fuel goes way down. I can easily say......3-4g off. Is it the winter fuel that's causing it or just the engine using more gas to get this engine all warm and toasty .
What's in winter fuel that makes MPG go down ?
- Thread starter chefwong
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i think it is ethanol or an alcohol that you northerners get put in your gas for the winter.
im glad we dont get that stuff here.
im glad we dont get that stuff here.
The oil in your engine/transmission and the grease in your wheel bearings is much thicker in cold weather, particularly during the warmup phase. Your tire pressure also drops by about 5 psi for every 10F drop in temps and many people never check it.
Use a 0w30 synthetic engine oil; synthetic transmission fluid and keep the car in a heated garage and you'll do much better ....
Use a 0w30 synthetic engine oil; synthetic transmission fluid and keep the car in a heated garage and you'll do much better ....
We got it year round here
One of the biggest reasons for poor MPG is the owner.
Tire pressure is lower when colder.
Warmup time is longer so remote starters waste gas for those that hate cold cars.
Engine runs richer longer as it warms up slowly until it reaches normal op temp.
IMO, I've seen other factors affect the MPG more than gasoline brand/type.
Tire pressure is lower when colder.
Warmup time is longer so remote starters waste gas for those that hate cold cars.
Engine runs richer longer as it warms up slowly until it reaches normal op temp.
IMO, I've seen other factors affect the MPG more than gasoline brand/type.
I don't have a lot of data, but my 94 Geo Prizm has only dropped 1-2 MPG in the winter vs the summer. The average over the last 10 months has been 32.4 MPG, and I'm probably getting 30-31MPG in the winter and 33-34 MPG in the summer.
You do have to look at long term numbers as I have the occassional tank that is 36+MPG. There are so many variables such as how full was the last fill up, vs the current. What about your driving, the weather, etc.
So I don't get too worried about one tank of fuel that is below 30MPG. It may have been a "short" last fill, or this fill was a bit more than most.
Obviously temperature has an impact as well as the driver behavior (warm up time.) This car sits outside, and instead of warming it up, I keep a space heater in the drivers floor board. The cord goes out the drivers door and connects to a heavy duty extension cord that is connected to a timer inside the house.
When I'm not on call, the timer is just set to turn on around 5AM and runs from 5AM until 7AM. If I'm on call, I have the heater run every other hour for an hour. I do the same if there is snow in the forecast so I don't need to clear the snow and ice from my car.
I recall reading that winter blend fuels contain about 3-5% less energy content, so that partially explains drops in MPG and I'm sure the longer times until a car goes into closed loop, cold lubricants, snow, and warmup factors probably account for the other 5% or so difference in fuel economy.
So, like many others have said, it's more than just the fuel that causes mileage to drop.
TB
You do have to look at long term numbers as I have the occassional tank that is 36+MPG. There are so many variables such as how full was the last fill up, vs the current. What about your driving, the weather, etc.
So I don't get too worried about one tank of fuel that is below 30MPG. It may have been a "short" last fill, or this fill was a bit more than most.
Obviously temperature has an impact as well as the driver behavior (warm up time.) This car sits outside, and instead of warming it up, I keep a space heater in the drivers floor board. The cord goes out the drivers door and connects to a heavy duty extension cord that is connected to a timer inside the house.
When I'm not on call, the timer is just set to turn on around 5AM and runs from 5AM until 7AM. If I'm on call, I have the heater run every other hour for an hour. I do the same if there is snow in the forecast so I don't need to clear the snow and ice from my car.
I recall reading that winter blend fuels contain about 3-5% less energy content, so that partially explains drops in MPG and I'm sure the longer times until a car goes into closed loop, cold lubricants, snow, and warmup factors probably account for the other 5% or so difference in fuel economy.
So, like many others have said, it's more than just the fuel that causes mileage to drop.
TB
Gasoline is supplied as winter & summer blends based on Reid vapor pressure. The winter blend is more volatile & evaporates easier to aide cold weather starting.
The drag caused by cold grease & fluids along with lower tire pressures all add up to a decreased mpg in the winter.
When I make a 250 mi trip to visit relatives in northern Wisconsin & the temp is near zero, my Chevy 4X4 always gets 3-5 mpg less than the same trip in summer.
The drag caused by cold grease & fluids along with lower tire pressures all add up to a decreased mpg in the winter.
When I make a 250 mi trip to visit relatives in northern Wisconsin & the temp is near zero, my Chevy 4X4 always gets 3-5 mpg less than the same trip in summer.
In some places, winter gas results in a noticeable decrease because oxygenates are introduced to control Carbon Monoxide emissions. Oxygenates used are generally MTBE and Ethanol. Neither has the energy content of regular gasoline, but ethanol has les than MTBE, resulting in greater drops.
All that being said, in many cases, both winter and summer fuels are oxygenated, and the decrease is due to a ton of other factors, which have been touched on in other posts.
All that being said, in many cases, both winter and summer fuels are oxygenated, and the decrease is due to a ton of other factors, which have been touched on in other posts.
I think the biggest difference (assuming you use the same gas brand, grade, etc.) is the amount of warm-up time in which the oil is stone cold. Likewise, the rapic cool-down that takes place after turning the engine off and repeating the long warm-up cycle again.
In Chicago, we've been running gas with 10% ethanol winter, spring, summer, fall for as long as I've been driving cars. Still, MPG will drop 2 or 3 MPG in the winter. Either there's still something different going on with the blend, or some other, incredibly constant variable is magically, consistently affected between the months of October and March. Conditions between those months can vary widely: 60 degrees down to -20, so I'm inclined to say it's something in the blend aside from oxygenates.
another difference is colder air is denser, also in many areas winter air is also dryer, 100% humidity air is 5/8 (almost half) the density of 0% humidity air (not sure if fuel injected cars with oxygen sensors will respond to humidity changes but I know carburated cars will)
so with a denser incoming air charge more fuel will be metered this is partially offset because it takes a smaller throttle opening to maintain speed but there is still some loss in efficiency
drag loads would also be more in colder/dryer air
I work at the airport next to a runway, in the summer here in GA we get high temps and humidity, the aircrafts engines produce less power and the wing needs more speed to produce lift there is a very large difference in amount runway used for a particular aircraft type
so with a denser incoming air charge more fuel will be metered this is partially offset because it takes a smaller throttle opening to maintain speed but there is still some loss in efficiency
drag loads would also be more in colder/dryer air
I work at the airport next to a runway, in the summer here in GA we get high temps and humidity, the aircrafts engines produce less power and the wing needs more speed to produce lift there is a very large difference in amount runway used for a particular aircraft type
The vapor pressure is probably the biggest culprit. Round September the gas starts to have more and more 'light ends' in it, until, in mid-winter, there can be ten percent Butane in your gasoline. The refinery loves that situation, as compared to summer, when they burn it for refinery fuel gas.
The Butane actually has a decent anti-knock index, around 113, but as javacontour says, WAY less energy content.
The Butane actually has a decent anti-knock index, around 113, but as javacontour says, WAY less energy content.
Being in NJ, we've had "winter formulated fuels" for many years now and yes, my mpg has always dropped off pretty significantly. I always attributed it to the winter fuel mixture but never once thought about the thicker lubes, greases etc in the engine causing more drag. Makes sense.
I check tire pressure once or twice a month and it is usually within 1-2 pounds of spec. I guess all the factors mentioned in this thread add up to a good 2-4 mpg drop off...at least for me.
Interesting thread!
Mikep
I check tire pressure once or twice a month and it is usually within 1-2 pounds of spec. I guess all the factors mentioned in this thread add up to a good 2-4 mpg drop off...at least for me.
Interesting thread!
Mikep
That indeed is true, colder air is more dense and as such the aircraft reaches its liftoff speed (which is ground speed) sooner and uses less runway, the indicated airspeed will remain the same in both situations. The engines will also produce more power as at each intake stroke there will be more air ingested. Low humidity and an area of high pressure will do the same but these do not have that effect as temperature does.
In fact, aircraft performance is measured against a standard atmosphere, 15c and 29.92", any deviation from that and performance is influenced.
John
[ February 27, 2004, 01:43 AM: Message edited by: JohnTDI ]
There is nothing magical in the blend - its all the other stuff that remains cold and drags your fuel mileage down, yes, consistantly in the the winter.
If you have a long term record of fuel mileage and dates, I'd be happy to show you how that directly relates to air temperature in your area. I've done that on my vehcile for the last three years and the fuel mileage directly coincides with the outdoor temps.
Its all the stuff that isnlt related to the fuel causing the drop - longer idle times, extended rich running in open loop while heating up, low air pressure in tires (unless checked), increased resitance from cold transmission fluid, increased resistance from gear oil, increased resistance from even grease in the driveline, etc...
I don't deny that there are other factors involved when it comes to cold-weather driving and MPG drops. However, we've been experiencing warmer than normal weather here in the midwest: mid-50s/low-60s, and the fresh tank I burned through shows the same MPG I've been experiencing. I can guarantee you that in a month, identical conditions -- weather, driving or otherwise -- will garner a 1-2 MPG increase in economy. I still say something else is going on with the "boutique blends" used around here in the winter. I think the previous post regarding vapor pressure is on the money.
There is something else. Winter blends have less energy content than summer. Check it out, it's right on the EPA website.
Remember also that since 1984 almost all cars sold in the US have had closed-loop O2 sensor ECU and smog systems.
What happens is that the O2 sensor 'sees' the extra O2 molecules in the exhaust stream, assumes the engine is leaning out and richens the mixture, worsening gas mileage [and increasing smog, but EPA denies it...].
Also ethanol at 10% and MTBE at 14%; typically mixed with pump rfg, has less caloric energy than the base gas, so you will use larger throttle openings to get the same power, also using more fuel in the process.
As others have pointed out, the thicker grease and longer warmup time to reach normal oil temps also increases engine friction and the tires lose pressure since most people do not re-check and fill them properly once it gets cold, so that adds to the rolling drag as well...
What happens is that the O2 sensor 'sees' the extra O2 molecules in the exhaust stream, assumes the engine is leaning out and richens the mixture, worsening gas mileage [and increasing smog, but EPA denies it...].
Also ethanol at 10% and MTBE at 14%; typically mixed with pump rfg, has less caloric energy than the base gas, so you will use larger throttle openings to get the same power, also using more fuel in the process.
As others have pointed out, the thicker grease and longer warmup time to reach normal oil temps also increases engine friction and the tires lose pressure since most people do not re-check and fill them properly once it gets cold, so that adds to the rolling drag as well...
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