Owners of diesel-powered vehicles may notice an issue starting their cars or experience under-performance during a cold snap, especially where temperatures drop below -7°C for several hours. What causes this phenomenon and what can vehicle owners do to stop this happening?
Vishal Premlall, Director of the South African Petroleum Retailers’ Association (SAPRA), a proud association of the RMI, says it’s important to understand how diesel functions in the vehicle and then steps can be taken to ensure vehicles perform optimally during exceptional cold spells.
“Diesel fuel is a very complex mixture of hydrocarbons that do not freeze when it cools down suddenly during very cold weather, but instead turn cloudy as very small wax crystals begin to form in the fuel and eventually thickens like soft jelly. This is known as diesel gelling. If further cooling takes place, diesel will be very difficult to pump through the fuel system of the vehicle. In extremely low temperatures it could freeze and become impassable through the fuel system,” he explains.
He recommends the following preventative steps:
• Most importantly, DO NOT use a heat source to heat diesel fuel systems. This can be extremely dangerous.
• Ensure that vehicles have clean fuel filters because wax crystals tend to easily block fuel filters that are already dirty. Regular vehicle maintenance at an RMI service provider is therefore very important.
• Ensure that vehicles are parked in a sheltered position overnight.
• If, under extremely cold conditions, the vehicle will not start at all, delay departure until later in the day when the ambient temperature has increased.
• Keep the fuel tank full as large volumes are less susceptible to diesel gelling.
• Avoid, where possible, re-fuelling diesel vehicles in warm areas and then overnighting or passing through colder regions. If at all possible, refuel in the cold region.
• Avoid refuelling from diesel tanks that are visible above the ground.
• If the vehicle starts, but does not perform satisfactorily, allow the vehicle to idle and build up heat in the fuel tank through circulation of hot fuel from the engine back to the fuel tank.
“We suggest that diesel-vehicle owners are mindful of the lowest ambient temperatures in their areas,” says Premlall.
In certain particularly cold areas, an additional additive is added to diesel fuel in order to avoid diesel gelling or freezing. In South Africa, winter grade diesel fuel is distributed through the retail fuel network from 1 April to 30 September.
“It’s important to take precautions to avoid problems associated with excessive diesel gelling or freezing as this can have a very severe impact on the operating system of the vehicle,” he says.