Winter diesel fuel
Below the cloud point the fuel begins to develop solid wax particles giving it a cloudy appearance.
The presence of solidified waxes thickens the oil and clogs fuel filters and injectors in engines.
Similarly the "Low Temperature Flow Test" (ASTM D4539[1]) indicates the winter performance of diesel with improver additives.
There are a number of solutions available which allow diesel engines to continue to operate in cold weather conditions.
[4] Note that a filter heater cannot melt wax particles in the feed system so that fuel supply can be problematic at cold start.
[4] In North America, gas stations offer two types of diesel fuel – according to ASTM D975[5] these are named No.
[6] For some diesel motors it is also possible to add even lighter fuels like gasoline to extend the CFPP characteristics.
Some car makers were recommending adding up to 20% gasoline to permit operation in cold weather (at the price of higher consumption) and it had been common practice in Europe where No.
Tests in the Alpine regions have shown that the diesel fuel offered at gas stations extends the law requirements by some degrees, showing a CFPP of −27 °C in all samples.
[9] The low cloud point (CP) of EN 590 ensures that wax particles do not precipitate to the bottom of the tank upon standing because daytime temperatures might melt them together.
Properties beyond Class 4 would require a kerosene type fuel with a low cetane number (at least 45 in EN 590).
The Australian Standard for Automotive Diesel AS 3570 specifies maximum limits for cloud point based on the 12 calendar months and the different climatic regions in Australia.
[15] At gas stations of the VanRaak group the winter diesel is offered at a CFPP –20 °C in the time frame from 1.
The Canadian General Standards Board publishes maps of common low temperatures for each region so that oil companies can adapt the diesel fuel accordingly, which they do about ten times per year.
[18] The time frames and minimum requirements for Czech winter diesel (směsné motorové nafty) is regulated by ČSN EN 590 offering the same classes as the European standard.
[26] The legal minimum time frames are usually extended by gas stations by a few weeks and in very cold winter conditions gas stations will switch to arctic winter diesel with a CFPP of –32 °C, in some regions even requiring arctic diesel atr –40 °C.
[30] Through different taxation the offered diesel fuel generally follows the extended specifications of the Swedish standard.
[31] The OKQ8 company offers two types depending on the region with currently two areas separated by the Dalälven river at 60° north latitude.
[36] In the United States there is no legislation on a fixed time frame when winter diesel must meet a specific temperature characteristic.
In regions with colder weather, most gas stations offer No.1 fuel at the same pump allowing drivers to decide for themselves on a winter blend.
