What is White Diesel and why do you need it for your Business?

DERV, also known as Road Diesel or White Diesel, stands for Diesel Engine Road Vehicle fuel is the highly refined, clear fuel you see at commercial pumps, often referred to as Ultra-Low Sulphur Diesel (ULSD). More than just a type of diesel, it’s the standard automotive diesel fuel sold at filling stations across the United Kingdom. Chemically, they are all the same and are a complex mixture of hydrocarbons, primarily paraffins, naphthenes (cycloalkanes), and aromatics, obtained from the distillation of crude oil. Its composition typically features hydrocarbon chains ranging from C₁₂ to C₂₀ with a boiling point between 170 and 360 °C. It’s purity is key, engineered for modern diesel engines.

Unlike some other diesel types like red diesel (gas oil), which is dyed red and used for off-road vehicles and machinery with a significantly lower tax rate, DERV, or White Diesel, is legally mandated for on-road use and thus carries the full rate of fuel duty plus Value Added Tax (VAT). As of 2022, the standard UK fuel duty rate was 52.95 pence per litre. This duty applies to every litre of  Road Diesel sold for on-road use.

DERV must meet the British Standard EN590, ensuring a minimum quality in terms of cetane number (indicating combustion quality), sulphur content (now ultra-low sulphur diesel – ULSD, which is essentially White Diesel), density, and cold-weather performance. To improve its properties, especially in colder temperatures, additives are often included to prevent waxing or gelling of the fuel. Furthermore, to comply with environmental regulations like the Renewable Transport Fuel Obligation (RTFO), DERV typically contains a percentage of biodiesel, specifically Fatty Acid Methyl Esters (FAME), usually up to 7%. This blend helps to reduce overall emissions but can also make the Road Diesel more susceptible to microbial contamination during long-term storage due to FAME’s hygroscopic nature. White Diesel is formulated to meet these stringent standards.

In essence DERV is the lifeblood of the UK’s road transport, powering everything from personal cars and vans to heavy goods vehicles and buses, adhering to strict legal and quality standards to ensure both performance and environmental consideration. As the commercially available on-road diesel, is crucial for logistics and transport. Crucially they are all fully duty-paid, making it the legally mandated fuel for today’s advanced diesel engines on UK roads.

The quality and performance of DERV are governed by a European standard adopted in the UK: BS EN 590. This is the single most important specification you need to be aware of when procuring fuel. It dictates the physical and chemical properties of all road diesel sold, ensuring interoperability across all vehicles and consistent performance.

Key parameters of the BS EN 590 standard diesel include:

• Sulphur Content: All DERV sold in the UK must be Ultra-Low Sulphur Diesel (ULSD), with a maximum sulphur content of 10 parts per million (ppm). This was mandated to reduce harmful emissions like sulphur dioxide, which contributes to acid rain, and to enable the use of advanced exhaust after-treatment systems like Diesel Particulate Filters (DPFs).
• Cetane Number: This is the diesel equivalent of octane in petrol. It measures the fuel’s ignition quality. A higher cetane number means the fuel ignites more quickly and burns more completely, leading to easier cold starts, smoother running, and lower emissions. The BS EN 590 standard specifies a minimum cetane number of 51.
• Biodiesel Content: The standard allows for a certain percentage of Fatty Acid Methyl Esters (FAME), a type of biodiesel, to be blended into the fuel. In the UK, DERV at the pump is typically ‘B7’, meaning it can contain up to 7% biodiesel. We will explore the implications of this later.

While the minimum cetane rating is 51, some suppliers offer ‘premium’ or ‘enhanced’ diesel with higher cetane numbers (typically 55 or more). For fleet managers, the benefit can be tangible: improved fuel economy (1-3%), reduced engine noise, and cleaner injectors. The incremental cost must be weighed against these potential savings and performance gains.

Furthermore, winter grade diesel fuel is supplied during colder months (typically November to March). This fuel is formulated with additives to improve its cold flow properties, preventing it from ‘waxing’ or gelling in low temperatures. The Cloud Point—the temperature at which wax crystals begin to form—is lowered, ensuring fuel can still flow through filters and fuel lines. Ensuring your supplier provides the correct seasonal grade is a critical, yet often overlooked, aspect of fleet reliability during winter. A unique insight for procurement managers is to query suppliers about their specific changeover dates for winter grade fuel and their cold filter plugging point (CFPP) specifications, as this can vary slightly between suppliers and regions, impacting fleet performance in harsh conditions.