Winterized diesel

Several people have said winterized diesel reduces fuel economy by up to 10%. I did some research on how refiners produce winterized diesel. The information below is from Chevron and Exxon.

There is a belief that diesel is winterized by adding kerosene. This is not true. Kerosene is a high sulfur fuel and does not have the characteristics that high speed diesel engines require. It is more cost effective to include additives that prevent fuel from solidifying, i.e., lowering the gel/cloud point. Blending low sulfur diesel #1 with the #2 diesel sold for vehicle use will lower the gel/cloud point although it is typically more expensive than using additives.

Exxon in its diesel fuel FAQ says "the use of Diesel Fuel No. 1 reduces power and fuel economy, and often is more expensive, so minimizing the amount of No. 1 Fuel in the blend is an important consideration."

If one were to add #1 diesel, refiners recommend blending no more than 20% #1 diesel which would lower the cloud point by about 5°F. This would decrease fuel economy by 1% as #1 diesel has 95% of the energy content of #2 diesel. You would also need to consider if the winterized fuel already has #1 diesel added.

Chevron says "When they work, additives have several advantages over dilution: they are readily available in most areas of the world, treatment cost is less, and the treatment does not lower fuel density (thus heating value and fuel economy are not affected)." (page 8 of Chevron's Diesel Fuels Technical Review)

Since additives can reduce the gel/cloud point by up to 50 to 70°F (30 to 40°C) (page 86 of Chevron's Diesel Fuels Technical Review), another cause of winter fuel woes must be considered, water in the fuel.

In the many years of driving a diesel and tracking fuel consumption I have not seen a noticeable drop in fuel economy. I have noticed that my TDI accelerates better in winter which is most likely due to colder air being denser. I live in Oregon's Willamette River valley where winter temperatures are in the 30s and 40s.

Software Mechanic said:

Chevron says "When they work, additives have several advantages over dilution: they are readily available in most areas of the world, treatment cost is less, and the treatment does not lower fuel density (thus heating value and fuel economy are not affected)." (page 8 of Chevron's Diesel Fuels Technical Review)

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Can anyone explain why Chevron put those three words at the beginning of their statement?

cp said:

Can anyone explain why Chevron put those three words at the beginning of their statement?

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I would guess because they start working at X-temperature, thus they are not working until needed

I noticed a big drop with the winter fuel.

I can tell you within a week of when they switched to the winter fuel, my mileage went from 50-51 mpg to 43-44 mpg. This is despite a new fuel filter and air cleaner. My driving habits have not changed and nothing else was done to the car. The guy I work with has an '06 silverado diesel and he's dropped from 18 mpg to 13 mpg. My older brother just picked up a '96 B4 TDI and he's gone from high 40's to 35 mpg, but we're still getting his car back to a maintenance positive condition.

cp said:

Can anyone explain why Chevron put those three words at the beginning of their statement?

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That's the ol' cover the ass statement.

Also, it makes me glad I've filled up with Chevron D2 a grand total of 0 times.

It will depend on many factors. Not all diesel supplies are from the same source and the winterization may be different. In addition cold weather reduces mileage so it can get rather confusing to really know.

Winter MPG drop

A little history.
This is the first winter that I have had Mobil 1 5W 40 light truck TD oil in my ALH TDI. From 5k to 100k I have used Mobil 1 0W 40 oil only.

In the winter coolent takes about 50% longer to come up to 190f (5 miles summer/10 miles winter).
Oil takes about 75% longer to get to only to about 180f. Normal summer oil temp is 200 to 210f. The engine has to do more work for a longer time with the colder/thicker oil just to run the oil pump, lower MPG. I have lost about 1 MPG with the 5W 40 this winter, 41 down to 40 MPG. I am going back to the Mobil 1 0W 40 at the 110K service.

I think that fuel temp. has more to do with the lower MPG then most would think. As we all know it will not take much to lower our MPG.
If the fuel is in a under grown tank will guess its temp is 50f and air temp is 75f (+ 33% temp) the fuel expanses with heat. This is a guess that 15 gal. of fuel will become 15.5 when it get to 75f. The reverse happens with a air temp 25f (-50% temp) the fuel contracts. Again this is a guess that 15 gal. of fuel will become 14.5 when it gets to 25f. From summer to winter we lose 1 gal. with exansetion and contraction.
Lets see if I can do this.
In the summer you can go 697.5 miles on a tank 15 gal.= 46.5 MPG
In the winter you can only go 652.5 miles on a tank 15 gal.= 43.5 MPG
In my guess 15 gal. became 15.5 gal. in the summer and 15 gal. became 14.5 in the winter.
Summer 697.5/ 15.5= 45 MPG
Winter 652.5/ 14.5= 45 MPG
It will not take much to lose 3 MPG (fuel) 1 to 2 more MPG (cold oil)

Walt

Software Mechanic said:

Since additives can reduce the gel/cloud point by up to 50 to 70°F (30 to 40°C) (page 86 of Chevron's Diesel Fuels Technical Review), another cause of winter fuel woes must be considered, water in the fuel.

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WOW, way wrong. Go back and re-read. The cloud point is lower 5-7, not 50-70. And that is if you use a cloud point reducing additive, which are expesive and high treatrates.

Most off the shelf additives are CFPP additives. Lowering CFPP 25-35 is possible, but not always the case. CFPP temperatures don't always equal operabilty. (In other words, just because you lowered the CFPP, it doesn't guarentee your car will start.)

Getting my car to start is harder, and I am doing lots of short trips, which means that extra energy is used in trying to heat the car as well as generate extra electricity just to try to make sure the battery is topped off.

It seems to me that my car is more difficult to start simply because it turns over more slowly in the cold.

If the fuel is indeed treated merely with additives, and it has basically the same energy density as summer fuel, then the behaviors I am doing at this point are causing my 15-20% drop in mileage for the winter months when coupled with the cold.

I used to see some drop in mileage in the winter, but it wasn't terrible. But now that I am experiencing much colder temps than in my previous experience, I am also seeing much lower mileage than ever.

So which is it, cold, fuel, or both?

I'll never really know from just arguing about it here.

I keep pretty careful records and this winter I've seen a 10% drop in MPG (was 48+, now 44 to 45). Last year, I did not have a drop, but the year before, I did. Driving style has been pretty consistant.

One difference: last year I used Castrol 0-30 European all winter. I think the lighter oil may make a difference.

The drop in the winter (true winter, not those wimpy Willamette valley 30s and 40s) (grin) is due to the temperature and not the fuel.

Actually 40 degrees seems to be the start of the sweet spot, up to the 70s and slow taper off there (people in real hot places find their fuel mileage goes down even without A/C as that take it out of the best range.

At real winter temps (20 and below) the engine heats up slower, glow plugs stay on longer, heavier use of heated seats, rear window defroster and mirror heat. Trany is cold and engine oil is cold, wheel grease in CV and wheel bearings is cold. All mean more drag. Even minor snow, ice ridges etc all contribute to the demise. Air is too cold and intercooler is making it worse, so combustion efficiency is down.

So, its not the winter fuel.

Can I prove it, yep. I go to work at 5:30 in the morning. Traffic is not an issue, and I can time light pretty well (not perfectly of course, but run the averages its pretty consistent). Upshot is, at -20, I see fuel economy drop to 25-28 range (and that's with the oil pan heater plugged in).

We get a shot of warm air off the Pacific and go into the 40s, and the fuel mileage goes up to 38.

Summer time, I see 35-40, with 38 a normal average.

So, its not the fuel, its what the cold does to your car.

Powder Hound said:

So which is it, cold, fuel, or both? .

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Both, but I would expect most of it to be the temperature. I will add that the oil companies don't change the fuel based on the temperature, they change the fuel based on seasonal expected temperatures. There would be no way they could adjust for an unexpected cold spell so they adjust for the coldest that would normally expected.

On short trips, yes. But I also notice a 10% increase in fuel consumption over long trips, when the cold start is no longer a factor.
So it's either the heat I request from the engine, or lower energy density in the fuel.

FOG, that doesn't make sense. Just because the fuel contracts in the cold doesn't take away its energy. So 15 gals become 14.5 gals, but the energy in them stays the same.

Additives are expensive, so it would make sense for refiners to keep more light hidrocarbons in the formulation and remove more paraffin, which reduces energy density. The idea that you can't blend "kerosene" because it is high-sulpher is, well, "not even wrong". Of course they don't blend kerosene after both D2 and D1 have been distilled, they just keep more of the D1-hidrocarbons in the D2 during the distillation. And clean up the Sulpher just the same.

I've documented a considerable drop in fuel economy in the cold from starter & glow plug drain on the electrical system . The recharge cycle pulls many amps increasing engine load using more fuel . Using a rolling start when it's cold can reduce recharge load by many factors lowering fuel use . I have records to prove this one also .

The point is anything you can do in the cold to reduce the amps pulled from the battery in the cold will help tank fuel economy . The more you do the more fuel is saved .

Short winter trips in real cold we've been having here lately definitely has been hurting my economy huge. Last fill-up my average was 38 MPG. Admittedly most times I have driven somewhere it has been in the -20 to -30 C range.

Last night on the way home it was -29 C and it took a good hour and a bit until the inside of the car was toasty warm. I also noticed that if I turned the fan speed up to 4, I could bring the coolant temp down .. Fan speed of 3 at that temperature outside seemed to be a good compromise. Coolant temp at normal and as much heat coming into the cabin as possible without dropping the coolant temp.

If I drive only in the city in this cold, it hurts economy even a bit more. I average around 46-48 MPG in summer, but around 51 MPG if I do a highway only trip.

I also notice though, as someone else mentioned, as soon as the winter blend fuel is at the stations, I notice an immediate drop in economy of about 10%, without the temperature changing. The huge temperature drop just hurts it more.

Spend the $100 or so and install coolant heater.Put one in last Friday and now only have to pre-heat for about 1 hr.Was -21C this morning,1hr 15 mins pre-heat,glowplugs came on for about 3 seconds,and approx 1.5 seconds of cranking.Slight smoke,no ough idle,no hesitation to start,292,000kms.
Food for thought

JASONP said:

Spend the $100 or so and install coolant heater.

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I live in Georgia, so my winter lows are in the teens, but it's far more likely to be in the mid-30s around here. However, I've got a short commute, and the mpg in the morning is often in the low 20s, as the engine is just barely warming up. I'm actually thinking about getting a frostheater, just for the mpg improvement. On the other hand, I wonder how much I'll actually save on fuel, vs how much I'd spend on the frostheater plus electricity?

What's an hour of hydro cost as opposed to short tripping a diesel,cold short drives are brutal an TDI's,increased coking, lack of lubrication,for me I think it was worth it.
Maybe I should attempt to do a short video of pre-heat vrs. no pre-heat

Smokerr said:

...people in real hot places find their fuel mileage goes down even without A/C as that take it out of the best range....

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I could never run without a/c in one of those real hot places (Phoenix) when it got hot, as I did not wish to degrade my interior due to excessive moisture incursion.

So when it did get hot, yes, there was another mileage decrease, but it was because a/c was on all the time.

The BTU content of a higher density ULS#2 (API gravity ~32) is 131,500 Net BTU/gallons. For a lower denisty ULS#1 (API ~ 41), it's 127,000,

There is a direct reltionship between BTU content and MPG. Switching from a ULS#2 to a straight ULS#1 (all other things equal) would decrease MPG by about 3.5%. Since most winter blends are 20% to 30% ULS#1, then, at most, you would expect about a 1% loss in MPG due to the lower density of ULS#1 deisel.

As mentioned above, additves will not change the BTU content, so they would not cause any drop in MPG.



Anything greater than 1% is temperture related and not the fuel.

Hm, OK, those numbers (assuming they're right) are compelling....

When you live where it can (and does) get really cold (cold doesn't even count until its a least -0F) additives alone in the "winterized" fuel aren't enough. Every fuel station with diesel around here is selling fuel with additives AND a blend of D2/D1, or for the commercial rigs, seperarate pumps with straight D1 and blended D2. Some post their "blend" ratio. Most are 30/70-30% D1 and 70% D2 with additives, some as high as 50?50 right now. Perhaps the station owners do this blending as its delivered to their location, I do not know. Just that it's standard procedure. It's been quite a cold spell, minus 30F and colder on and off for several weeks. Add a bit of Power Service white bottle and no issues with normal pump fuel.... yet.
Most of the mpg loss no doubt is due to increased frictional losses of thick greases/oils in wheel bearings, CV joints, transaxles, engine oils, etc. not to mention increased alternator loads, but to say there is NO, or even only 1%, loss due to fuel dilution is unrealalistic. I chart all my tanks, and even though I don't get a huge drop in the "cold", (my above freezing mpg average is 52 and right now the last two tanks have been 47ish, which is around 10-12%). It is more than a 1% drop as soon as the "winterized" fuel starts in the fall (usually the end of Oct. here) when the temps are still quite tolerable. Certainly where I live isn't anywhere near the coldest place on earth (it just feels like it this year) but don't believe that "additive only" D2 is the only fuel supplied for cold weather.
(edit)
Vehicle referenced above is garaged in unheated area where temps do not fall below 10F at morning start-nor is the ZeroStart heater being plugged in. So while its not near as cold as ambient, it isn't warm at start up either.

jettawreck said:

When you live where it can (and does) get really cold (cold doesn't even count until its a least -0F) additives alone in the "winterized" fuel aren't enough. Every fuel station with diesel around here is selling fuel with additives AND a blend of D2/D1, or for the commercial rigs, seperarate pumps with straight D1 and blended D2. Some post their "blend" ratio. Most are 30/70-30% D1 and 70% D2 with additives, some as high as 50?50 right now. Perhaps the station owners do this blending as its delivered to their location, I do not know.

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For folks in the Snow Belt, if temps are forecast to drop below about +10°F, I think it makes sense to ask before you fill up at a strange pump.

We typically advise new TDI owners to fill up at busy stations, the ones which get frequent deliveries of fresh fuel. But at this time of year, that is not enough. I know of stations separated by not too many miles, which sell fuel that has at least a 20° difference in cloud point/gel point.

Many or perhaps most of the OTR trucks have fuel heaters, so they can run straight #2 diesel and not have to worry about gelling. It is the local organizations and companies, the municipalities with their snow plows and the school districts with their buses, that must have reliably winterized fuel. Find out where they get their fuel. Or wait a few more weeks -- spring is on its way.

wolfskin said:

FOG, that doesn't make sense. Just because the fuel contracts in the cold doesn't take away its energy. So 15 gals become 14.5 gals, but the energy in them stays the same.

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Energy content is not the same. Fuel is sold to the user on a volume basis, not weight. You get 231 cubic inches (1 gallon) of fuel for the stated price. The amount of BTUs that fit into that 231 cubic inches is a function of temperature.

Additives are expensive, so it would make sense for refiners to keep more light hidrocarbons in the formulation and remove more paraffin, which reduces energy density. The idea that you can't blend "kerosene" because it is high-sulpher is, well, "not even wrong". Of course they don't blend kerosene after both D2 and D1 have been distilled, they just keep more of the D1-hidrocarbons in the D2 during the distillation. And clean up the Sulpher just the same.

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Additives are cheap compared to blending.

Well, OK, when you buy it.
But if anything, denser cold fuel should bring you more BTU per gallon, not less, right? So you would get more miles per gallon, not less.
Yet, that's contrary to observation.

How could additives be cheap compared to tweaking the distillation process. D1 and D2 don't come separated. They are separated in the refinery, by directing different distillation fractions to different mixers in a proportion that can be finely tuned. This is where the "blending" occurs. They don't produce D1 and D2 and then blend. They produce the right mix of hydrocarbons directly in the refinery.

TornadoRed said:

For folks in the Snow Belt, if temps are forecast to drop below about +10°F, I think it makes sense to ask before you fill up at a strange pump.

We typically advise new TDI owners to fill up at busy stations, the ones which get frequent deliveries of fresh fuel. But at this time of year, that is not enough. I know of stations separated by not too many miles, which sell fuel that has at least a 20° difference in cloud point/gel point.

Or wait a few more weeks -- spring is on its way.

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Good advise!! Except for that last line.....
No spring here 'till mid April. LOL
I'm headed out on Saturday for ten days for some summer. Fly to P.Rico, cruise to Barbados and island hop back to P.R. The wife booked the trip when I went to Michigan snowmobiling. It's been a long cold stretch!!

wolfskin said:

Well, OK, when you buy it.
But if anything, denser cold fuel should bring you more BTU per gallon, not less, right? So you would get more miles per gallon, not less.
Yet, that's contrary to observation.

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The volume change in fuel due to temperature is very, very trivial.

How could additives be cheap compared to tweaking the distillation process. D1 and D2 don't come separated. They are separated in the refinery, by directing different distillation fractions to different mixers in a proportion that can be finely tuned. This is where the "blending" occurs. They don't produce D1 and D2 and then blend. They produce the right mix of hydrocarbons directly in the refinery.

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A small tweak at a refinery processing a hundred thousand barrels per day is very costly.

jettawreck said:

Good advise!! Except for that last line.....
No spring here 'till mid April. LOL
I'm headed out on Saturday for ten days for some summer. Fly to P.Rico, cruise to Barbados and island hop back to P.R. The wife booked the trip when I went to Michigan snowmobiling. It's been a long cold stretch!!

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if you have time while in P.R. I recommend you check this out:
http://www.naic.edu/
http://en.wikipedia.org/wiki/Arecibbservatory
it was in the Bond movie Goldeneye, although they say it is in Costa Rica it is not. it's a really cool drive out there from San Juan. also, the fort in San Juan is a must see. did you snowmobile up en da UP, eh? best trail system I've ever seen

Sip'n Diesel said:

did you snowmobile up en da UP, eh? best trail system I've ever seen

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+1 to da snowmobilin

It's really awesome, nothing else like it.

Keeweenaw, specifically