Does COLD weather affect MPG???

I laughed every time I had to shift when it was colder than -10. It was much harder than normal and even the shift gate didn't want to move. Above that temp it was perfect. Also, the intake temp at around -10 was around 8 above. I'm assuming that was post intercooler and the water temp was 197. This was off the OBD port using my iPhone.

Something is just different with my car now, it's hovering around plus 20 here and I'm still getting 35 mpg on 30+ mile drives. Takes 3 miles to warmup fully.

Also I was an intern at the DOT this summer and heard that alot of the problems with rutting in anchorage isn't studs, it's the sublayer of silt that pretty much all of anchorage is built on. Some bad decisions on materials were also used in constructing the roads. In front of sears on the Glenn for example is 4 or so different test strips of different materials. Next time you go by, you can see that some lanes are severly rutted and others are barely touched. But I agree that studs have an impact, I also believe that stud>studless always on ice. My 4wd expedition just had BFGs year round and was fine, but doesn't compare to my traction now. If they could make a studdless compound that didn't get worse after a year then I might bite.

The wife runs studded nokians on her Impala now but think we will try blizzaks next time. Funny you had shifting issues at -10 we never noticed anything right down to -40. Must be different oil in my tranny.

Manual? I heard blizzacks were the best thing in the world till about 2k miles or so.
MikeInAnchorage runs a really cool tire. For some reason the name escapes me but it has bits of carbide imbedded in it and he's really happy with them.

jettawreck said:

Agree w/most of the above, except:
"Even if #1 fuel is mixed with #2 fuel to help winterize it, I'm not so sure #1 fuel really has a LOWER energy content."
I think the reference material has an error.
Pretty sure that #1 fuel has lower energy/BTU content. Produces less heat in a furnace, too. Any experienced diesel owner will avoid it except when needed. Costs more and delivers less MPG.

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I looked again and figured out the problem. Pound for pound, #1 and #2 are nearly identical in terms of heating value. But on a volume basis, (like when we fill the tank), they are different, because #1 weighs between 6.87 to 6.71 lb/gal and #2 weighs 7.39 to 6.87 lb/gal.

That being said if you convert the heating values to a volumetric basis, and average the range for the two fuels you get 134,212 Btu/gal for #1 and 138,826 Btu/gal for #2. Still not really a big difference, roughly 3.5%. If you were to consider 3.5% less mpg on a car that can get 50 mpg, we're talking 1.75 mpg due to lower energy. Interesting.

Turbosprężarka said:

I looked again and figured out the problem. Pound for pound, #1 and #2 are nearly identical in terms of heating value. But on a volume basis, (like when we fill the tank), they are different, because #1 weighs between 6.87 to 6.71 lb/gal and #2 weighs 7.39 to 6.87 lb/gal.

That being said if you convert the heating values to a volumetric basis, and average the range for the two fuels you get 134,212 Btu/gal for #1 and 138,826 Btu/gal for #2. Still not really a big difference, roughly 3.5%. If you were to consider 3.5% less mpg on a car that can get 50 mpg, we're talking 1.75 mpg due to lower energy. Interesting.

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I've done those calculations before and come up with the same numbers. Then considering that most poeple don't run straight #1, but a 10-30% blend of #1 into #2, the drop in BTU is about 1% or less due to winterized fuel.

Every credible study I have seen shows that BTU and fuel economy are well correlated. 1% drop in BTU = 1% drop in MPG.

Energy content of diesel #1 (either blended at the refinery or by the vehicle owner) is just a small part of the hit in fuel economy during the winter.

Turbosprężarka said:

.....
That being said if you convert the heating values to a volumetric basis, and average the range for the two fuels you get 134,212 Btu/gal for #1 and 138,826 Btu/gal for #2. Still not really a big difference, roughly 3.5%. If you were to consider 3.5% less mpg on a car that can get 50 mpg, we're talking 1.75 mpg due to lower energy. Interesting.

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Agree.
Like I had said per post #21:
"I think you attribute way too much loss to "winterized" fuel. The energy content isn't 10% less, more like less than 5%, but the other cold weather factors contribute most to the mileage drop. I've run winter fuel in the warm weather and then the mileage drop is very little."

I dropped from 42 down to 38mpg as the temp dropped into the teens here in Maine. I was surprised at the drop, but after reading above, it seems logical. I intend to make up some of this by slowing down a little to compensate. I think I will just set the cruise at 62 and see if I can get back a couple mpgs.

I've never seen a noticable drop in mileage in the Winter on any diesel vehicle I've owned over the last 23 years. Temps down around 14F and the two 09 Jetta's we have still average around 40 to 42 mpg. Same as the rest of the year.

Dweisel

I just ordered a front grill cover for the TDI since I have been having much longer than normal warmups and also seeing a decrease in MPG now that winter is here. Ordered from https://www.worldimpex.com/item_detail.html?sku=272153 This is my first winter season with the TDI.

Let's not forget the increased rollng resistance when there is slush, snow or ice on the road. That also forces you to operate in a sub-optimum RPM regime that pushes MPG down.