[allan5oh]

Thought I'd post it here too:

Filter Council

Q: What is the "cloud point" of diesel fuel and why is it important to filtration? A: #2 diesel fuel has a wax component that contributes to the lubricity and heat value of the fuel. The "cloud point" refers to the temperature when the wax precipitates out of the fuel in the form of small wax crystals. Different fuel blends can have very different cloud point temperatures, generally ranging from -10°F to +40°F. #1 diesel fuel does not contain large amounts of wax, and therefore does not have a noticeable cloud point. Diesel fuel distributors blend local diesel fuel supplies so that the cloud point is usually not reached. However, if ambient temperatures fall below the cloud point of the fuel on a vehicle, the precipitated wax crystals can quickly coat and plug a filter element.
To avoid filter wax plugging and loss of engine power, diesel fuel filter systems are often supplied with an auxiliary fuel heating or return fuel heat recovery systems. Fuel additives are also available that modify the formation of wax crystals, making them less likely to plug the filter.

Q: Should I use diesel fuel additives?

A: Always follow the equipment or engine manufacturers' recommendations for the use of fuel additives. Note that alcohol based additives will degrade fuel/water separator performance.

cloud point = "gelling". It's not the gelling or thickening that's the problem, it's the wax that plugs the filters. If the fuel reaches the pour point, then it is basically solid. But usually the filters will plug before this happens.

Notice how the article states #1 has almost no chance of wax forming, yet additives "may" reduce the formation of wax in #2. I know which I'd prefer.

FAQ

What is low-temperature operability? Low-temperature operability is a diesel fuel’s ability to perform at low temperatures. All petroleum distillate products contain waxy materials, which, at low temperatures, can crystallize and plug fuel filters. The cloud point of the fuel measures the first appearance of the waxes, although filter plugging will not typically occur until the ambient temperature is 5° to 10°F below the cloud point. There are several approaches, both operational and fuel-related, to ensure proper operability in cold weather. Vehicle-related approaches include the use of fuel heaters, keeping the engine running, parking the vehicle in heated areas, etc. Each of these is designed to keep the fuel warm, above the point where waxing occurs. But each of these approaches has obvious drawbacks, as well.

The low-temperature operability of the fuel can be adjusted in several ways, as well. Blending a No. 2 fuel with No. 1 can lower its cloud point; this has traditionally been the most common approach to dealing with winter operability. But, 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. Another approach to reduce the filter plugging incidence is to use wax-modifying additives. These additives can give operability benefits equivalent to No. 1 Fuel blending without the power and fuel economy losses. Use of wax-modifying additives is generally the approach for ULSD No. 2.

Note that, especially early in the winter season, water buildup in vehicle tanks, when it freezes, can also plug fuel filters or fuel lines. If you experience filter plugging problems when the ambient temperatures are between 10° and 30°F, the most likely cause is water, not the fuel itself.

What should I do in the winter to adjust for the cold temperatures?
We recommend that you purchase a diesel fuel that has been winterized for your area by mixing it with Diesel Fuel No. 1 or low-temperature fluidity improver additives. Non-winterized diesel fuel will not generally cause problems as long as temperatures are at or above 10°F. The addition of about 15% to 20% Diesel Fuel No. 1 to Diesel Fuel No. 2 will reduce the cloud point of the fuel by about 5°F.

We offer winterized product in a majority of markets that experience severe weather conditions. If temperatures fall well below norms for the local area or you will be driving much farther north, additional Diesel Fuel No. 1 blending is recommended.

Why shouldn’t I just use Diesel Fuel No. 1?
While Diesel Fuel No. 1 has an advantage in low temperature operability, there are some disadvantages, as well. The energy content of Diesel Fuel No. 1 is about 95% that of Diesel Fuel No. 2 and will provide a correspondingly lower fuel economy. Diesel Fuel No. 1 is also lower in viscosity and provides less lubrication for the fuel pump and fuel distributor.

Trucking Software by ProMiles / Fuel Gelling Technology Solutions

...In blending, it is useful to know that No. 1 diesel is a refinery stock that is similar to kerosene and jet fuel. It has excellent winter operability because the cloud point is extremely low, typically in the range of -40°F.....

http://www.filtercouncil.org/techdata/tsbs/91-1R3.pdf

In that PDF it states #2 has a cloud point from -18F to +20F. #1 has a cloud point of -40 at all times. So let's see, first we don't know the cloud point of #2, and we don't know how much additives will affect it. So it could be anywhere from +20F to -30F or so with additive, but we don't know. We're guessing how much additive to add. Not only that, #2 will always be thicker then #1.

http://www.todaystrucking.com/images...lems91-1R2.pdf

....The Pour Point is the temperature at which the paraffin in the fuel has crystallized to the point where the fuel gels and becomes resistant to flow. Pour points also vary but they usually occur from 10°F (5.6°C) to 20°F (11.1°C) below the cloud point....

yikes, sounds scary to me. Additives do NOT modify the cloud point.

A Word of Caution: Never add gasoline or alcohol to diesel fuel to help with cold weather operation. The practice creates an explosion danger and will damage the fuel injection system

Interesting, I've also seen the math that gasoline does not affect pour point/cloud point as much as some believe.

Cold Flow Improvers The only way to actually lower the cloud point temperature is to dilute #2 diesel with #1 diesel or kerosene. However, this lowers the fuel heat value and can be an expensive solution. Alternately, widely available cold flow improvement additives may help delay filter plugging. They lower the pour point of diesel fuel several degrees, but do not change the cloud point temperature. Instead, cold flow improvers work by altering the paraffin crystal shapes to needle-like forms. More of the needle-shaped crystals can pass through the filter element, slowing the plugging process.

Let's see, avoid the situation altogether running #1, OR delay it by modifying the shape of the wax, yet the cloud point and pour point are barely modified. #1 is superior to #2 with additives.

[allan5oh]

I still stand by my thought that water is more of a problem. At least up here. We generally run #1 from November to April or so. There is no #2 available up here during that time. Most trucks I've seen broken down had an empty fuel filter, indicating that ice has blocked the line. This is where proper maintenance comes in.

[GMAN]

Water can be a big problem at any time. That is why I usually keep spare fuel filter in my trucks. It is much less costly to put a filter on the truck than wait for road service and have to pay them several hundred dollars to do the same thing. It has been some years since I have had a problem with gelling, but not so with water. Just earlier this year I got some water in my fuel somewhere. I thought that I had lost an injector. I put in some chemicals, changed the filter a couple of times and problem solved.

[tracer]

One hard lesson I learned about treating diesel fuel in winter - if you suspect it's going to be cold during the night, always drain water from the primary fuel filter/water separator (if you have one). I once failed to do this when the night temperature dropped to 16F (minus 10 C) and the water at the bottom of the filter froze - the engine refused to start. Also, another tip is never leave tanks half full when it's really cold. frost will appear on the inner sides of the tank, and after it turns into water once the engine heats up, all this water will go into the engine and the truck can just die on the highway (happened to me - 0.5 mi from the terminal; $350 towing bill). Curious fact: idling all night doesn't prevent fuel from gelling when it's extremely cold. I once was sitting at a Flying J in Winnipeg, MB, Canada and it was -40C (same in F). I didn't put in any anti-gels in the tank as I was idling all night (too cold for the Webasto). In the morning I drove to the exit of the truck stop and ... the engine died. Back then I was a company driver, so the towing bill was paid by Challenger Motor Freight

[rank]

I've never heard of anyone burning #1 here (Kingston, ON). Don't even know where I would buy it except maybe from a heating oil retailers. I suppose that's the stuff they call stove oil that they sell you if you have your oil tank outside the house?

How does #1 lubricate?

[allan5oh]

rank, AFAIK, most of Canada switches over to either a #1 blend, or full #1. I'm pretty sure in the prairies it's full #1.

[rank]

So if #1 doesn't cloud due to the lack of lubricating wax, how does #1 lubricate? Do you guys use an additive out there to replace the lost lube qualities?

[allan5oh]

Commercially sold #1 has additives that make up for the lack of lubricity. Kerosone does not.