Winter diesel fuel
 

Does anybody have any real data on the FE effects of winter diesel fuel vs. summer diesel fuel. I've been hearing all this stuff over at Cummins Forum (which generally could care less about FE) about how much the winter fuel kills FE. As far as I can tell, all the "evidence" anecdotal.

For me, I have seen my mileage come down some in the last few months, but pretty much what I'd expect due solely to the weather (low temps, windy, etc.). Granted, the last time I filled up was Nov 8, so maybe I don't have winter fuel. I asked the attendant at the time whether their diesel was winterized. She kinda had this puzzled look on her face and said, "We don't add anything so it so...(shrug) No?"

I'm filling up tonight/tomorrow morning so we'll see if there's a change then. The other day when I was at another station filling up my wife's car I saw they had a sticker indicating the diesel was winterized. I didn't notice any sticker at my station, but I assume they have to have switched to winter diesel by now.

Anyway, I'm wondering whether the winter diesel makes any difference or if it's just the winter that's making the difference. Any thoughts/data?

I just filled recently with mostly ULSD for the cold snap we had. Despite the cold and low percentage of biodiesel (B50-> B20), I still can make 41 mpg. I do not see the hit, even with my EGR temporarily disabled (warm up time takes forever).

I did some more looking to see if I could find any references for energy content differences. This site cites a 4% lower energy content for winter blend (mainly due to density).
Why do an analysis of diesel fuel

Obviously cetane and other things affect mileage slightly too, but heating value is the biggest thing. IMO, it's really hard to see a 4% difference given variations in weather, fill variation, traffic, driving habits, etc.

I am on my 3rd diesel truck and I have yet to notice an MPG difference between winter and summer blends. Not like I do in the gassers.

I am trying a few things I learned over at a Kenworth site that mentions some tips on diesel fuel economy driving. Worth a shot anyway. Link: Kenworth Fuel Economy White Paper

I get a huge swing on my diesel from summer to winter, sure the fuel has less energy but the cold itself has a big effect as well as it takes forever to warm the engine up.

This is mainly a complaint from big trucks, IMO. The little yard apes just started repeating it for their honkin' big ol pickemups . . as coolant temps tell most of the story. It is hard to keep the heat in the cab flowing without a winter front in some Class 8 I've driven. So I tend to think that with coolant temps kept high, the small variations introduced by winter fuel (or anti-gel products) is confined to those who track mpg by the tenths. IOW, not as great a change as to ethanol-free gasoline, but with some of the same effect. I wouldn't try to control for it, just for:

- failure to bring truck to op temp (fluids, greases, tires)

- coolant temps kept high

- increased idle time

We see some of the same problem in summer what with trying to keep the cab cool, thus increased idle time (reduced average mph, why I'm big on that number). Winter is definitely a rolling resistance problem, from all aspects of road, load & weather. Cumulative. If coolant temp is low, we know the other temps are also too low for best friction reduction. Plus cold air density ain't favorable to highway speeds. Etc.

I also think that only a rough estimation of percentage loss is possible. So long as nothing (nothing) changes on the commute year-to-year, then one can predict for that vehicle used that way with that load on those roads. Harder to use as a cross-reference for others (except, maybe, as a minimum).

So, Minimum Man what are the opening & closing dates for "winter fuel" in your area, and can you give us that minimized percentage loss in the time period covered? (Walk on water again, DD, all winter)

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I filled up this morning. Same station, different attendant. I asked this one if their diesel was winterized. She smiled and said, "Honestly I have no idea!"

At this point I gotta think everybody has switched over. I'm trying to find out exactly when they introduce it, but no luck yet. I'm not positive whether ther could be station-to-station variation or if everybody's the same.

Wouldn't you know I ran across a chart showing the calendar for the US for the changeover in the past few days . . and have since been unable to remember where. Only thing close was a quote of a quote by BP saying that blend becomes more "winterized" from September up north to later starting dates south, and maximizes in Jan/Feb, then tapering into May (sooner, farther south). Might as well concede that "summer" -- Memorial Day into Labor Day -- is one assured of non-blended fuel, overall.

Would be nice to see that calendar again, and to use an E-W Interstate as divider between N-S to get the "blend times" down to a fixed, short period.



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I live in Indiana and I don’t think they sell much in the way of winter blend here. I’ve had tanks gel up (“cloud” is the ASTM term) at 7 below here. Maybe at big truck stops up along the Indiana Toll road that serve trucks that may go farther north, but few other places here.

As for the heat content of winter blend, it is proportional to the No. 1 content. The heat value of straight No. 2 is 139,000 BTU/gal. For No. 1 the heat content is 130,000 BTU/gal. So if you winter blend were the outstanding stuff you get in Nebraska and the Dakotas (66% No.1) you get a heating value of 135,900 Btu/gal or about 2% lower heating value.

Most stations that sell real winter blend are quite proud of it (it sells at a considerable premium) so if you have to ask, it probably isn’t winter blend.

Now the decrease in MPG is very real, but I’d ascribe the reduction mostly to increased aero drag.

Remember the part of the road load equation that deals with aero drag.

HPaero = kρCdAV3 where
K is the consolidated conversion constant
Ρ is air density
Cd is coefficient of drag
A is frontal area
V is velocity
From standard psychrometric tables we see that:
At 0°F ρ=603.7 grains/ft3
At 70°F ρ=520.0 grains/ft3

We see that when air temperature drops from 70 to 0 the air density increases by 16.1% and thus the biggest component of road load goes up by the same amount.

Winter blend MPG loss = 2%
Denser air MPG loss = 16%

Winter has other effects that I cannot quantify.
a. Increased rolling resistance from snowy/slushy road surfaces
b. Driving conditions (including other drivers) make hypermiling difficult

I get about 10% lower mileage with winter diesel. Its also quite noticeable when I get the switch because my power drops a lot.