Home Forums Gear Hunting Trucks and Four-Wheel Drives Why does you fuel mileage decrease in the winter?

First of all let's quantify Winter. Zero degrees or less in portions of the country where winter blend fuel is different that summer blend.

My fuel mileage takes a nose dive every winter by 2-3 MPG. I am curious as to the root cause. Is the decrease caused by the additives and alcohol in the winter blend gas. Or is it the result of a cold engine running less efficiently than a hot one. Could it be a combination of the two. And no i do not start my vehicle and let it warm up for five minutes or so before driving. and yes I do use synthetic oil.

Let the discussion begin.

Meanwhile it's -12 outside and I am arm wrestling the gas needle every time I drive.

Ya, 13-14 mpg summer and 10-11 mpg winter in my truck.

The rolling resistances of your bearings and tires increase with cold temperatures so it requires more energy to move the vehicle.Cold air is also denser so there is more resistance to the vehicle moving through it at highway speeds.Thirdly,if your vehicle has a choke,or enrichening system for the fuel injection system they will be functioning more which will burn more fuel.

Wouldn't the cooler, denser air enabling a more efficient burn negate the minimal effects of driving through the increased resistance?
I love it when I go to work in the morning and the truck wobbles for about a mile from the frozen tires. <img src="/ubbthreads/images/graemlins/crazy.gif" alt="" />

Rdinak,

I'm sure the other factors mentioned play a role too, but you hit the nail - it's the oxygenated fuel.

Oxygenates, containing MTBE or ethanol, contain less energy than non-oxygenated fuel. Oxygenated fuels result in lower carbon monoxide emissions.

Carbon monoxide emissions are more of a factor during the winter due to cold weather and temperature inversions.

yup, 2-3 mpg (frrom 27 to 24). The air density and cold starts have something to do with it, but even on long runs, the fuel economy stays poor. Even out here in the boonies, but I do believe most of our gas is formulated for Salt Lake, which has a heck of an inversion problem. FWIW, Dutch.

My truck loses mileage and gains mileage every year at about the exact time they increase the additives

Actually as the air becomes colder and therefore denser you have to add more fuel to maintain the air/fuel ratio.You can make more power with denser air but you must add more fuel in order to do it.
It is currently -30F where I live and you can really notice just how much more the engine has to work to get the vehicle rolling in these temperatures.

Funny-after it drops to -20 or so your vehicle has a new set strange noises everytime you start and stop.

Interesting discussion on a topic that I have observed for years. Curious is it better or worse on the deisel engines vs. gas.

RD

I always thought it was because I warm the truck up for 10-15 minutes before driving it, and often use 4wd. Not to mention driving through snow is akin to going up hill, ie more work for the engine.

If you lock it in 4wd for the duration of winter, it'll definately suck more gas then in 2wd.

rd.........as far as diesel versus the gassers , the diesel will still have to overcome all the factors mentioned same as a gas engine , plus you will need to run lighter fuel in extreme cold instead of #2 . The winter blended diesel fuel has less energy content than #2 so you take a fuel economy hit from that as well .

That all said ,my Dodge can still hang to about 17 mpg for all around winter driving........

It's the hibernation factor. As winter approaches men start to eat more to make it through the winter; eat more=more weight. More weight=less mileage.
batch

I have questions also on older cars that are warmed up on cold days you do not see the typical moisture coming out
of the exaust? I wonder if the sensors are geared more to a
moderate climate on the newer vehicles. I see about a 3 MPG
decrease in mileage in the winter over the summer?

In a nutshell, catalytic converters oxidize unburned hydrocarbons and carbon monoxide into water and carbon dioxide.

Older cars without catalytic converters will show less "moisture" out the tale pipe, as will older cars where the converter is losing its efficiency.

My guess would be it was because of tire slipage on the road, moist air usualy creats a hydrgen rich fuel giving better economy. Try some of the old watter injection systems.

Phil

Sure my gas consumption increases in the winter...Granny Low in 4x4 has a habit of sucking up gas...

(When it is 35 below (F) with 21 inches of snow on the ground and 4-foot drifts, that is a good gear...)

All the fluids are solids in the winter, so nothing rolls as easily. ricciardelli hit the nail on the head. When it hits 35 or 40 below everything burns more gas.

If you want better mileage move to Canada. The gallon is 160 ounces! <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> Course the gas price is $4.00 a gallon, so I guess it still costs more.

Doesn't it have something to do with the volatility of the fuel as well? The lower the temperature, the less easily vapors are going to be made from the fuel and it is the vapors that burn, not the liquid itself. Since your whole gas tank and lines are not insulated at all, it wouldn't matter how warm your engine was since the ambient temperature still makes the fuel cold before it hits the carbs or injectors. I think that this combined with the fact that all of your engine oil and transmission fluid will be thicker, you warm your engine up longer, and the whole dense air/fuel ratio combine to drop the efficiency. When you think about it, a 2-3 mpg isn't to bad in these adverse conditions...

SS

Winter gasoline does have a slightly different blend. The "light off" temperature is lower...otherwise you would never get the engine started.

Amazing now that its 60 degrees my GMC 2500HD has improved fuel mileage by almost 3 miles per gallon at $2.09 per gallon very little bit helps.