MPG decrease in very cold weather??

[Triple_Se7en]

Originally Posted by 2009Caraman
I'm kinda new to driving and was wondering what kind of penalty I can expect in extremely cold weather(-20c sustained)? Drives are typically 15mins or less.

I replaced my lower intake manifold gasket and though performance has returned fuel economy has slightly dropped. It's only been a 1/2 tank though and since i did the repair it's been at least -15c every day. I'd like to hear your thoughts or observations on mileage in the cold.

Real cold weather affects almost everything. It even affects slow transportation, like daily walks in below freezing temps. Our breathing gets affected during brisk walks in cold temps, which in-turn affects our oxygen level in our lungs.
You get less MPG. I get less TWO OH'.....lol

My dog never complains during those long walks thou. But he didn't smoke menthol cigs for one-half of his life either.....

 

[Quattro Pete]

Originally Posted by PimTac
This must be a older car? I haven't taken precautions like that in a long long time.
It applies to all cars/engines, old or new. In cold weather, on a cold engine there is little heat to go around. If you take it away from the engine by pumping it into the cabin, then the engine will take longer to heat itself up.

That's why automatic HVAC systems wait a while before ramping up heat blowing in cold weather on a cold engine.

 

[Jackson_Slugger]

Another factor is driving through significant snow accumulation, I find that kills mileage the most...

 

[PimTac]

Originally Posted by Quattro Pete
Originally Posted by PimTac
This must be a older car? I haven't taken precautions like that in a long long time.
It applies to all cars/engines, old or new. In cold weather, on a cold engine there is little heat to go around. If you take it away from the engine by pumping it into the cabin, then the engine will take longer to heat itself up.

That's why automatic HVAC systems wait a while before ramping up heat blowing in cold weather on a cold engine.





Good point. I guess that's why modern cars are electrified all around with heated windows and mirrors and heated seats and steering wheel. You don't notice that cold air blowing as much when your bum is toasty.

 

[maxdustington]

Originally Posted by edyvw
Whatever you do, first few km's do not turn on heat and vent for 2-3km's as that delays warming up. Also, do not idle longer than necessary to put seatbelt, get accomodated. Move and move slowly, allowing transmission (assuming it is automatic) to [censored] around 2,000rpms.
Move somewhere cold and try that. Everyone always says not to idle to warm up forget that you need to see out of your windshield in order to drive your car. What are you expected to do, drive slowly with the windows down until your car heats up? You can't drive slowly like that if you live anywhere near a city.

 

[hummdrumm]

Originally Posted by JLTD
All of the above, plus don't forget that before fully warmed you burn more fuel as well.


This. It may be altitude as well. But consider two extremes in different climates. I have lived in LV and Great Falls. In LV my daily commute around 20 miles at 45 degrees. GF between 10 to minus where ever. Low for me in in 7 years -38 and 4 miles daily. Another factor was auto start which I didn't have. Friends that had it often set theirs for 2, sometimes 3 starts a night

 

[RDY4WAR]

Originally Posted by maxdustington
Originally Posted by edyvw
Whatever you do, first few km's do not turn on heat and vent for 2-3km's as that delays warming up. Also, do not idle longer than necessary to put seatbelt, get accomodated. Move and move slowly, allowing transmission (assuming it is automatic) to [censored] around 2,000rpms.
Move somewhere cold and try that. Everyone always says not to idle to warm up forget that you need to see out of your windshield in order to drive your car. What are you expected to do, drive slowly with the windows down until your car heats up? You can't drive slowly like that if you live anywhere near a city.


There's products out there that work very well at preventing fogging/frosting on the inside of the windshield. A good waxing of the windshield helps keep the frost on the outside from setting up too much. A pot of cold water takes care of what's left. This is what I did when I lived in Ohio, and it worked fine. I would always wait until the temp needle started to move before I turned on the heater. It would only blow cold air before that point anyway.

 

[4WD]

Originally Posted by Jackson_Slugger
Another factor is driving through significant snow accumulation, I find that kills mileage the most...


HaHa … same with mud and sand …

 

[barryh]

Here's 12 years of data which if you ignore a slight rising trend shows a regular as clockwork 10 MPG or 15% swing between summer and winter on my air cooled motorcycle. With no control of cooling, air cooled engine's never really get up to temperature in the winter so I would expect a water cooled engine to fair a little better.

 

[fdcg27]

So you're looking at around -4F?
I'd expect a very noticeable increase in fuel consumption, in the range of 10-20% or at least that's what I've come to expect with various vehicles over the years.
At that kind of start temperature, I'd surely let the thing idle at least ten minutes prior to setting out if only for the comfort of the driver.
That's what I do, since I don't intend to layer up as I do for a planned extended time outdoors in the cold just for the drive to work.
There's also the need to have enough heat available to avoid the moisture in your breath freezing on the windows.

 

[BrianF]

Ball park with my trailblazer I was running about 12.6 L/100km in the summer. Come this cold winter I average around 15. Yes there is more idle time included but there is nothing I can do about it.

 

[2009Caraman]

OP here. Thanks for the comments. Vehicle is a 3.3l 2009 Caravan. After doing some math it seems it has fallen 2 mpg since the deep freeze started. Nothing crazy so I will take it as it is.

These vans are pretty bad on fuel to begin with. Went from 17mpg to 15mpg is all. All city stop and go driving.

 

[Luftmasse]

Yes it does. Especially with the winter blended gasoline.

 

[Pew]

Originally Posted by Quattro Pete
Originally Posted by PimTac
This must be a older car? I haven't taken precautions like that in a long long time.
It applies to all cars/engines, old or new. In cold weather, on a cold engine there is little heat to go around. If you take it away from the engine by pumping it into the cabin, then the engine will take longer to heat itself up.

That's why automatic HVAC systems wait a while before ramping up heat blowing in cold weather on a cold engine.



Mine doesn't even warm up to operating temps once the temps dip below freezing unless I start going up hills. Mileage drops a good 5 MPGs.

 

[Railrust]

I tend to drop at least 2 mpg's as soon as the weather turns cold where I am (usually November till March).

I attribute it to the colder air density, and the computer having to add more fuel to keep the air fuel ratio 14.7 to 1. Could be wrong.

 

[kschachn]

Here is an article from Scientific American, kind of old but probably still relevant:

https://www.scientificamerican.com/article/why-is-the-fuel-economy-o/

 

[Bryanccfshr]

Colder weather means a vehicle has to overcome
Thicker engine oil, thicker transmission fluid or oil/ thicker transaxle or differential oil.

The shorter the trip the more the impact cold weather will have on overall MPGs. As the fluids may never actually get up in temperature.

Additionally more accessories are used, defrost, heaters, seat heaters etc drawing more power.

At highway speeds you deal with more wind drag from denser air and the cold air flowing keeps the differentials cooler, meaning it would never be as efficient as on a warm day,

All of these inefficiencies mean More fuel is burned and that is why many locales require oxygenates to deal with the air quality issues that causes in denser areas.

 

[edyvw]

Originally Posted by maxdustington
Originally Posted by edyvw
Whatever you do, first few km's do not turn on heat and vent for 2-3km's as that delays warming up. Also, do not idle longer than necessary to put seatbelt, get accomodated. Move and move slowly, allowing transmission (assuming it is automatic) to [censored] around 2,000rpms.
Move somewhere cold and try that. Everyone always says not to idle to warm up forget that you need to see out of your windshield in order to drive your car. What are you expected to do, drive slowly with the windows down until your car heats up? You can't drive slowly like that if you live anywhere near a city.

Really? I regularly park at -20c below while ski, sometimes overnight at parkings and it reaches to -35c occasionally. I live 1.30hrs from the coldest area in lower 48, South Park basin. Now, if I have kids with me, that is different story. But if not, I start it, get adjusted and off to go. If ice on the car, I scrape it.

 

[edyvw]

Originally Posted by PimTac


This must be a older car? I haven't taken precautions like that in a long long time.

I do that with every car. Especially with two small kids. In VW I need to keep it on cold and no vent for a 1-2 miles, and after will have good heat. Same with BMW. Sienna is hopeless case even with block heater.
Turning heat on and than ventilation, you are basically cooling down coolant that is going through heater core. I tell visitors here when they drive to the Pikes Peak: Turn off A/C, turn on heat to max and vent to max, otherwise you might be overheating somewhere at 13,000ft.

 

[supton]

What's so hard about an ice scraper and cracking a window? That is what I do, unless if there was a storm and I have an inch of ice; in that case yeah I'll let it idle so as to soften the ice. But for frost? scrape and motor off.

I leave the heat off until I see the temp gauge move. Is it hurting anything to turn the heat on full blast right after getting in? Nope. Technically the heater core acts like a mini-radiator (same principle) only the real radiator has a thermostat that won't open when the coolant is below a temperature around boiling--but the heater core gets coolant always, so turning on the heater fan is going to slow down engine heating up. Does it really matter? I'm not sure--the engine will warm up faster with it off, but once on, it's still drawing heat away, so I'm not sure it matters... me, I just don't want cold air blowing on me, so I wait until I know it'll be warm air blowing on me.

My truck drops mpg badly in winter. I drove it year round once and could hit 20 mpg, 21 even, in summer. Snow tires and winter dropped it to 16 mpg. Although now that I drive it little it seems to get 16 year round... my other cars will drop in cold weather but it seems like, if it's above 20F I don't have much of a change. But for me, a short trip is 15 minutes, most trips are much longer--once up to temp, winter losses are not massive.

IIRC winter blend gas often has a bit less Btu's per gallon, so there's something like up to 5% there (but it varies with the blend).