[Ian Williams]

Does anyone have a rule of thumb for how much your mileage goes down as it gets colder?

Like X mpg for Y Temp

[allan5oh]

I don't know, but close to a full mpg here. We're talking from 70-80 degrees to -10 or so F. every 10 F is about .1 mpg. Of course that depends on wind too. Once it gets real cold that wind really can pound you.

[wot i life]

My old boss in Wales said that by fitting wind deflectors on the truck, he reduced fuel consumptiom by 5%. I,m no engineer and I don,t know much about drag co-effecient, but I do know he wouldn,t lie about that. :wink:

[Dejanh]

I hauled 5000LB load from L.A. to Chicago and burned about the same amount of fuel as i would hauling a 45000 due to wind.....i just hate driving while windy but dont have a choice..

[bob h]

The slight increase in air density is a factor, but the main cause of fuel economy loss (up to about 1 mpg) in winter is due to lower btu content of winter fuel... not the temperature.

[solo379]

10-15% is about a norm. Lot's of factors, winter blend, air density, longer time to get to "operating" temperature(tranny, axles..)... :roll:

[yoopr]

no rule of thumb from me but I always expected from a 1/2 to a gallon mpg decrease

[allan5oh]

No, it's mostly due to the air. I run #2 a lot in winter, and it doesn't make a huge difference. Maybe 10-15% compared to the cold weather. It does make a difference though.

There's also the extra friction from the tires hitting the pavement, diffs being cold, transmission cold, all the wheel bearings are stiff.

[bob h]

quote="allan5oh"No, it's mostly due to the air.

I believe it's as much (or more) due to idling and cold engine operation IMO

I run #2 a lot in winter,

If you're running #2 in the winter, you must be way farther south than me... if you don't run blended winter fuel here, you'll freeze up

and it doesn't make a huge difference. Maybe 10-15% compared to the cold weather.

could you elaborate on this statement, not sure what it means? maybe i'm still asleep ;0)

It does make a difference though.

There's also the extra friction from the tires hitting the pavement, diffs being cold, transmission cold, all the wheel bearings are stiff.

we have had mild ambient temps here up until about 3 weeks ago (rarely went below 30 degrees), since then the temps have plumetted and stayed cold (rarley rises above 5 degrees)

my fuel mileage has not changed significantly since the temp change... however, it did change more significantly when the winter fuel started being delivered in the fall (over 1/2 mpg)

[allan5oh]

But one thing though... our diesels actually become more efficient when its colder out. Easiest way to tell is how much power it has. It's never going to inject "more" fuel at WOT+full boost. It always injects the same. If it pulls harder in winter, it's creating more horsepower with the same fuel. It becomes more efficient.

However, you're right when you compare the two one day to the next. I was talking overall, in winter the big difference is the extra friction and air resistance.

I just got back from a trip, I fueled up with #2 in Minnesota. It's -35 with the windchill here. I would never run more then 50% #2 when it's this cold. Hell, it even has that 2% biodiesel crap. No problems. Still not much of an improvement in fuel mileage compared to the Canadian fuel I had in there. I think I went from 5.8 to 6.5. But I also went from 42,000 lbs with the canadian fuel to empty and 16,000 with the #2. I also went from going with the wind to going against the wind.

I think the #1 problem guys have with "gelling up" is water in the fuel. Almost all the time the guys are blaming the "crap american fuel" that they have to buy down south. I think it's from going from a very humid/warm climate to a very cold dry climate fast. The water condenses out of the air in the tanks, and collects on the inside of the tank. Next time they fill up, trouble is a brewing! Don't you think it's funny how must trucks die shortly after fueling up, even with good Canadian fuel?