Here in SE Virginia, our summers typically hover in the 90's and the winters in the 40's. Each year we typically get a good cols snap and it drops in the teens at night and 20's-30's during the day.

Earlier this winter we had a week long episode of colder than normal weather which hung in the low 30's all day and teens at night.

The avg MPG's on my truck for mixed driving dropped from the 18+ that I normally enjoy to around 16.5. When the weather returned to normal for us, my MPG's returned to normal as well.

Have any of you noticed any serious climatic swings in your MPG's?

Yes, I know that vehicles normally burn more fuel in the winter but the info screen on my truck drives that point home.

 

Tim, remember that it's not just the environmental conditions that affects MPG. It's also the winter blend fuel, extra load (heater, defroster, heated seats), denser air, typically longer warm-ups/idle time, longer time to operating temp, etc.

I typically see a 1-2 MPG drop, but this winter has been pretty mild (I'm near Charlotte, NC) and I haven't seen much of a drop at all. Myabe .5-.75 based on my calculations.

But, I don't warm up the truck and we've had very little frost so I have barely run the rear window defroster. I have however used the heated seats.

 

Tim,

What you describe jives with what we see up here. Once we get the winter blended fuels, our mileage typicaly drops a couple numbers.

My exploder gets pretty close to 18mpg on the highway in the summer, but the best i can usually do in the winter is about 16mpg. If i drive it to work when it is really cold (below zero for highs) I sometimes get 10mpg or so because of the idle time.

they say that you don't need to idle them ... but at -29F ... yeah ... i idle for 20 minutes or so.

 

I've seen the drop in mpg from winter fuel. Anyone know what's different about "winter" fuel? Is it really necessary?

 

I believe the governement requires a higher ethanol content in the winter time, it's to help alleviate air pollution that gets trapped closer to ground level during the colder months.

I drive an SVT Focus and I've noticed a difference in mileage every winter when the fuel blend is changed.



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Google is your friend! (I expect better from a sponsor.)

Here is an explanation of Summer Vs Winter fuel blends; HowStuffWorks "Summer-grade versus Winter-grade Fuel"


During the summer, pollution is a frequent concern due to increased levels of smog and ozone, which can harm the lungs. Summer heat boosts the formation of ozone, while the appearance of an inversion layer -- an immobile layer of air -- can trap pollutants in the lower atmosphere

Summer-grade fuel has a different Reid Vapor Pressure (RVP) than winter-grade fuel, which contributes to its being (marginally) more eco-friendly. RVP is the vapor pressure of gasoline measured at 100 degrees Fahrenheit

Because RVP standards are higher during the winter, winter-grade fuel uses more butane, with its high RVP of 52 PSI, as an additive. Butane is inexpensive and plentiful, contributing to lower prices. Summer-grade fuel might still use butane, but in lower quantities -- around 2 percent of a blend

......when do companies start producing these different summer fuels? The EPA defines April to June as the "transition season" for fuel production [Source: EPA]. Refineries switch over to summer-blend production in March and April [Source: EPA]. Gas stations have by June 1 to switch to selling summer-grade gas, while terminals and other facilities "upstream" from pumping stations have to switch by May 1 [Source: EPA]. Following the summer driving season, companies switch back to winter blends beginning in September, with the first winter increase in RVP allowance occurring on Sep. 15.

Because of the way winter and summer fuels react under different atmospheric pressures, particularly in terms of evaporation, it's important to use summer and winter fuels during their respective seasons. Fuel that's stored out of season can evaporate. It can also hurt engine performance.

 

Fuel blend is a factor, warm up and idle time is a factor and air temp and density is a factor. Cold air is more dense...the computer recognizes this and adds fuel to the mixture, lowering your MPG. The side benefit to cold dense air, is HP.

It all adds up and like others posting here, I usually see a reduction of 1 - 2 MPG during the winter months.

 

OK cool, thanks guys for the in depth posts. I never idle to warm up unless I'm completely iced over.

 

I've found that I'm balancing out close to the summer months this winter. I'm attributing it to the fact that I travel A LOT more highway miles than I have previously. That may not be it at all, but I'm going with it.

 

I was just thinking about this a few days ago and and one thing that came to mind is the air is denser during the winter. More dense air equals more resistance and more drag. Cold air makes more power but is less efficient. Warm air makes less power but is more efficient. Can anybody verify this?

 

yep, I see the same thing here in the Chicago area every winter. about a 2mpg drop is pretty typical for me.

 

I may be a little off base but I think Tim's comment was based on what I tend to see which is:
Winter time (so your already running winter fuel).
Truck warmed up already (so rich condition until engine warm is over with)
Driving down the road (so no idling to warm the engine and traffic conditions eliminated).

My ecoboost seems to get better fuel economy in 55 degree conditions than 45 degree conditions.
Driving down a 4 lane road that I travel a lot at 65 mph. Instantaneous gauge will hover at 19 on a nice warmer day. Will hover at 17 on a colder day.

Just seems that the colder air causes it to run richer for some reason and burn more fuel for the same driving conditions. I have noticed it numerous times this winter.