NickB79

I have ~5500 miles on my 2005 xA, and during the summer it was averaging 33-34 mpg. Now that winter has set in here (Twin Cities, Minnesota) I'm lucky if I get 30 mpg per tank. Usually it is 27-29 mpg, with a 50/50 mix of city and highway driving.

The temps have been really cold lately (it was -10F a couple nights ago) and it takes a long time for the low coolant temp light to go off. Is it normal for my mileage to decrease so dramatically in cold temps?

Why exactly does my mileage go down in winter? I let it run about 5 minutes before shifting out of park whenever I start up, but 10-15 minutes a day running in park could make that much of a difference?

lissy

Yep. From ~41 Mpg all highway to ~37 Mpg so far this Winter.

neotim

Also, I remember someone mentioning that some gas companies use a different additive mixture in the winter which results in lower mileage.

5C10N_DR1V3R

Here's what some metro a$$clowns have to say about it. Most of it makes sense.

Low tire pressure
Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure source). Fuel economy declines 0.4 percent for every 1 psi drop (source).

Increased rolling resistance
Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).

Crappy road conditions
It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)

Lower average engine temperature
In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.

A block heater can offset this problem somewhat, as can garage parking, or combining trips (to minimize the number of cold/hot cycles).

Also related...

Higher average lubricant viscosity
Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.

Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.

Weaker gasoline
Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a litre of winter gas as you will on a liter of summer gas. (Source.)

Higher electrical loads
In colder temps, you use electrical accessories more often:

- lights (in higher lattitudes it's darker in the winter)
- rear window defroster (because it's easier than using the ice scraper, right?)
- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions)
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)

More aerodynamic drag
No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).

A vehicle’s aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% (source).

source:
http://www.metrompg.com/posts/winter-mpg.htm

flyerI

All of the above posters make good points. The biggest use of gasoline is letting the engine idle for the longer periods before you start moving. I saw an article on this some years ago. Essentially it said for the best mileage and without compromising the longevity of the engine you should let the engine idle at normal speed for about 1 to 2 min in extremely cold temps and then begin driving. Drive very easy, no hard acceleration. The engine will come up to normal temp much quicker and less fuel will be consumed.

Kremtok

Very good, very thorough explanation, 5C10N_DR1V3R; it matches everything I've heard/read about cold weather driving. Thanks for that!

NickB79

That all made a lot of sense. And I feel like a moron because I totally forgot to check the PSI on my tires this winter.

Here in MN, we are required to use a 10% ethanol blend in all gasoline except premium blends (91+ octane). I wonder if that contributes as well.

dgHotLava

yes, in winter the refineries add more chemicals to the fuel...the cemicals do lower MPG slightly...(at least up north they do)

all of the other items are logical, combined they will make a big diff.

lalagimp

I was wondering about this myself but wasn't sure where to post.

I'm in Southern California where we really do not even get that cold, but I'm still suffering this season.

For the last month or so I've been getting around 27mpg instead of 29-32mpg. My driving conditioned haven't changed.

This may have been the case on other vehicles I've owned, but maybe that I didn't know my MPG numbers so well that I could watch and tell a difference on the tanks with such confidence.

dexter_5000

yeah this is true we talked about in engine repair theory this couple of minutes is to allow the engine to pump oil and circulate it through. also setting your air to re-circulate helps in warm up time. using the ac in winter is aslo helpful since it removes moisture from the incoming or re-circulating air.

Macster

Yeah i went from mid 30s to high 20s to low 30s.. lowest so far when it was in the 10s got around 23...

jdmotorsports

i use my remote start almost every night at work. i'de rather waste the little bit of gas then drive with cold fluids and a cold cabin.

dgHotLava

actually, the best way to warm up a car is to start driving it right away...that way all the fluids warm up together.

remote starting does not warm up the transmission (or differential fluid in a rear wheel drive car). two out of three ain't bad....

i do agree getting into a warm car on a cold day is nice...

TJ

I think it's the ethanol based fuel in the winter blend here in Reno. I've got consistent lower mpg's the past two winters.

Tomas

See also THIS THREAD:

https://www.scionlife.com/forums/vie...=asc&&start=75

Yes, even the "warm climate states" have winter and summer fuels...

Just because it doesn't drop to freezing temps doesn't mean there isn't a 20-30 degree change in the environment, and that requires a different fuel mix...

The information is out there.

Sciond

I just had my car up north.....going to NYC averaged 33 mpg...coming back 25mpg...maybe it was the gas......my driving styke did not change all other variables were constant except air temp....

Ghost_1

Don't forget that while the blue "cold temp." light is on the xA/xB does not have overdrive engaged. So essentially the transmission shifting times are different. They take a little longer to shift, allowing the engine to rev at higher RPM's thus burning a little more fuel then usual.

Cars generally require more fuel to be thron into the engine during cold tempuratures for start up. Also when depending on the viscocity/thickness of the oil will affect how much harder the engine has to work to get warmed up and to start up. If you have less then approximately 30-40k miles stick with 5w-30. I hit 20k and started using 10w-30 and I noticed the engine takes a little more to start up in colder tempuratures. . .usually when it's 38 or below.

gslippy

Yes. My "normal" MPG has dropped from about 29-31 to 25-27 in the coldest weather. I'd say 10% isn't a bad loss for such cold temperatures (Pennsylvania). Some loss is to be expected.

dchichaz

Does anyone know if there is a way to stop this from happening? I want the engine to shift like normal even when it's cold.

I don't want to debate the finer points of why or why not this should happen, just do you know if it can be stopped.

Ghost_1

I don't think you can. As far as I have read it is part of the way the car was designed. . .which I guess means the ECU is pre programmed that way.