All diesel fuel inherently has water in it. That is why your truck has a fuel/water separator built into the fuel filter assembly that you periodically have to drain.
Two things happen to diesel fuel in the cold. 1) The paraffin (petroleum wax) component of the diesel fuel will polymer together, forming a wax layer in your fuel. This is called gelling. Once the paraffin wax forms, it is very hard to reintegrate back into the fuel. This wax will clog your lift pump and fuel filter, leaving you dead on the side of the road. 2) The water component in the fuel, which is impossible to avoid with diesel fuel in most cases, will turn into ice. Since fuel and water do not mix, the water component will separate out in your tank. As this turns into ice, the ice crystals stack up on the the filter face, causing filter icing. This will also prevent fuel flow and starve your engine of fuel.
So, any wise diesel owner should do three things in the winter:
1) Always carry a spare fuel filter in your truck for roadside emergency use.
2) Run an anti-gel diesel fuel additive that prevent paraffin wax polymerization, but also has a deicer that prevents ice crystal buildup.
LINK: AMSOIL Diesel Concentrate with Cold Flow Improver
3) Keep 1 bottle of fuel reintegration emergency additive in the truck. This is smart to have in case you do have a gel or ice issue, it can reintegrate the fuel.
LINK: AMSOIL Diesel Recovery Emergency Fuel Treatment
Ensuring that you run an anti-gel in the winter will keep you on the road by preventing gelling and icing.
Anti-gel explained:
Wax forms plate like structures (flat) and AMSOIL Cold Flow breaks those up, more like strings, so fuel can flow through. It modifies the wax crystals to allow the fuel to pass through filters, and prevent premature plugging due to gel. It also works well with biodiesel blends as well. Biodiesel has horrible cold temperature properties in general, and the use of a biodiesel-compatible product will help lower the point at which the fuel clouds, or begins to gel. Biodiesel or B100 does not contain paraffin since it is not petroleum based. When B100 gets cold crystals do appear and they act like wax in that they stick together and are large enough to plug filters. These crystals form sooner or at higher temperatures and are larger in size in B100 than in regular diesel fuel. Biodiesel is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats which conform to ASTM D6751 specifications for use in diesel engines. The saturated compounds in the Biodiesel form the crystals that plug filters. When they form they are larger than diesel wax crystals. Most anti-gels, including AMSOIL's, work best on biodiesel fuels B20 and less.
The key to messing with paraffin wax gel is to disrupt it from agglomerating together into a “glob” that is big enough to plug a filter and or fuel line. A copolymer chemical with molecular chains similar in size and distribution to paraffin co-crystalize with the wax and disrupt the crystal formation, thereby allowing your fuel to continue to flow through your fuel filter and keep you on the road.
As diesel fuel cools you will notice a white haze or cloud in the fuel. This usually happens around +10 degrees F. but can happen at higher or lower temperatures depending on fuel characteristics. The white cloud or haze is caused by wax crystals precipitating (coming out of solution) out of the fuel and becomes visible. When fuel warms above the Cloud Point of the fuel, the white appearance will disappear as wax crystals dissolve back into the fuel. The use of an anti-gel usually does not change the Cloud Point of a fuel, and if it does it is usually only by a few degrees. There are however some Cloud Point depressants that can significantly reduce the Cloud Point of a fuel. Cloud Point depressants will adversely affect anti-gels or Pour Point Depressants, however. Anti-gels typically affect the CFPP (cold filter plugging point) and Pour Points of a fuel. Anti-gels work on the wax crystals in the fuel. As the wax crystals form or come out of solution, the anti-gel will modify the wax crystals so they are smaller, will not stick together and will continue to flow through the filter in much lower temperatures than untreated fuel.
ULTRA-LOW-SULFUR DIESEL FUEL CHALLENGES
The reduced sulfur levels in modern ultra-low-sulfur diesel fuel (ULSD) result in reduced lubricity, the property that controls wear in the fuel injectors and fuel pump. Improving lubricity in ULSD is difficult because it must be done without adding sulfur back into the fuel. Additionally, ULSD is subjected to extensive refining, making it even more difficult to treat. For these reasons, many competitive claims are not based on ULSD fuels, rendering them inaccurate and irrelevant. AMSOIL Diesel Concentrate Plus Cold Flow Improver is formulated specifically for modern ULSD fuel. It improves lubricity, helps maintain engine oil TBN and prevents soot loading.
SUPERIOR COLD-WEATHER PERFORMANCE
As the temperature drops, the wax naturally found in diesel fuel begins to form crystals. The point at which wax crystals form is known as the cloud point. These wax crystals eventually clog the fuel filter and starve the engine of fuel, preventing it from starting. While low quality fuels may form wax crystals in temperatures as warm as 40°F (4°C), most fuels have a cloud point near 32°F (0°C). The point at which the wax crystals clog the fuel filter is known as the cold filter-plugging point (CFPP). AMSOIL Diesel Concentrate Plus Cold Flow Improver lowers the CFPP by as much as 34°F (19°C) in ULSD.
It also reduces the pour-point temperature of treated diesel fuel, providing better fuel delivery to the injectors during cold weather. It is formulated with a jet-fuel-type deicer that disperses water to control ice formation in all sections of the fuel system. Diesel Concentrate Plus Cold Flow Improver minimizes the need for the use of #1 diesel fuel, enabling better fuel economy, performance and lubricity.
POUR POINT VS. CFPP
It is important to distinguish between CFPP and pour point. Many competitors make great claims regarding pour point, leading consumers to believe their products are superior when they actually have an inferior CFPP. Once fuel surpasses its cloud point, the wax crystals begin to clog the fuel filter. The CFPP temperature is a more important characteristic than pour point because the engine will not run if fuel cannot pass through the fuel filter.
