Parts of Germany saw temperatures drop to -28°C (-18°F) this week, well below the point at which diesel begins to crystalize. Although gas stations in the country are legally obligated to offer a special weather-resistant form of the fuel from mid-November to late February, most forms available in Germany are only designed to withstand temperatures above -23°C (-8°F).
"The lack of adequate winter-proof diesel is a problem," Izabela Grzywacz of ADAC's Berlin office told SmartPlanet, explaining that German law only requires fueling stations to offer 'winter diesel' made for a minimum of -20°C (-4°F) in the cold months.
Unlike gasoline, which remains a liquid until about -45°C (-49°F), standard diesel fuel can begin to crystalize around 0° (32°F). Although diesel-vehicle owners in Austria and Scandinavia usually have access to 'polar fuel', which withstands temperatures as low as -40°C (-40°F), this special type of the fuel is scarce in Germany.
"We are pushing for the government to lower the legal threshold to -30 degrees (-22F)," Grzywacz said. "Not only is it clear that these kinds of temperatures return every few years, but cars with diesel engines are only one problem; transport trucks also run on diesel and are often parked outdoors."
Most of the reported stalled-vehicle incidents have occurred in eastern and high-altitude regions of the country, which have borne the brunt of a heavy Siberian front. According to the country's trade daily Handelsblatt, hundreds of vehicles have been affected by the deep freeze, with assistance services such as those offered by ADAC unable to provide little more than a tow to a warm garage.
The German automobile association also advises drivers against some common mistakes including mixing gasoline with diesel fuel, which could cause engine damage, and trying to manually defrost a fuel tank, which can quickly become a fire hazard. Instead experts say the safest and most reliable option is to have the vehicle towed indoors where the tank can thaw out naturally and paraffin crystals in the diesel can return to liquid form. A fuel filter change is also recommended.