As if we really needed another reason to hate winter.
Those of us living in northern climes have already started to notice the seasonal decline in fuel economy, even with careful attention to sagging tire pressure (probably the best known effect of the mercury's slide).
Yet, despite diligent all-around maintenance and continued careful driving, cold weather fuel consumption can be dramatically worse than in warm temperatures.
How much worse?
Have a gander at these calculations for a Honda Civic hybrid at 60 MPH in varying ambient temperatures:
Look at the extremes: the coldest MPG is 28% lower than the warmest. (Source.)
My own experience supports this: 12.5% worse mileage during the colder half of the year (Oct 15 to Apr 15) than for the warmest half (Apr 15 - Oct 15), on average 2002-2004 in my 1989 Accord. Comparing just the warmest months (Jun-Aug) to the coldest (Dec-Feb), the difference is even more apparent - 21.2% worse (2002).
Why so bad? Off the top of my head, I could think of a couple of reasons to explain it, but together they didn't seem significant enough to account for the magnitude of the change. With this mystery to solve, I hit Google. And here's what I learned...
9 reasons your winter fuel economy bites
1. More idling
This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.
Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).
2. 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).
3. 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).
4. 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.)
5. 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 (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).
6. 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.
7. 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 liter of winter gas as you will on a liter of summer gas. (Source.)
8. 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); heated seats/mirrors
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)
9. 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).
Only one disagreement.9 Reasons Why Your Winter Fuel Economy Bites!
An idling engine gets 0 mpg.
Idling engine gets 0mpg.Only one disagreement.
An idling engine gets negative miles per gallon.
When you're at a stoplight (the longer the better) watch your gas mileage drop as the seconds go by.
An engine that is not running gets 0 mpg.
Wasn't my bible by the way, wasn't my post! I just thought it had a lot of plausible reasons and was impressed with the depth.I revisited your BIBLE for reasons and it is probably the idling that is hurting my FE. You will see me cross the finish line with vigor as victor when my new CVT Honda will get 35 CITY MPG in my 100% CITY driving. I will be yelling "C'mon..." as I see you in my rearview non-dimming mirror at you murmuring marty marty marty
Well...if all variables are truly the same you're no doubt simply hallucinating. More likely you're just a troll.I have an EX with CVT and mileage has dropped from about 425 miles per thank to just under 300. All variables are the same and I can't figure why I'd see a 30% drop. Any guidance would be helpful.
I was surprised to see sub6 seconds 0-60 on the Accord V6.Does the 6AT with the VCM and DI really get sub 6 0-60 numbers. If so, wonder why that does not get more pub. Sub 6 numbers were the holy grail of this class so I am surprised this does not get more media if indeed it is true.
As my car is new with 550 miles on it, I haven't totally floored the accel and redlined the car yet with a stopwatch and measured myself. I've heard stats that say it is around 5.7 or 5.8 secs. All I know is the car is fast in acceleration and has lots of power and torque, and is much smoother than the CVT. I drove the CVT too. It is nice, just not as smooth and powerful.Does the 6AT with the VCM and DI really get sub 6 0-60 numbers. If so, wonder why that does not get more pub. Sub 6 numbers were the holy grail of this class so I am surprised this does not get more media if indeed it is true.
I don’t believe the V6 has direct injection. It still uses multiport but still makes the Accord fast. As far as publicity goes, there are many V6 family cars today that are 6.0 seconds to 60 or less - Camry, Accord, Passat , Altima, Maxima, Mazda6, Charger, Impala, Legacy Turbo just to name a few. With today’s new technology it is expected.Does the 6AT with the VCM and DI really get sub 6 0-60 numbers. If so, wonder why that does not get more pub. Sub 6 numbers were the holy grail of this class so I am surprised this does not get more media if indeed it is true.
Don't overlook the significance of tire pressure (#2 on the list). When the temps dropped from the 60's to the 30's in a matter of days, my mileage dropped from ~32 to ~28. I blamed it on the cold, and the winter gas, but a week later i noticed my tire pressure was in the high-20's on all 4 tires (usually low-mid 30's).I have an EX with CVT and mileage has dropped from about 425 miles per thank to just under 300. All variables are the same and I can't figure why I'd see a 30% drop. Any guidance would be helpful.