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Red Diesel: A Guide to Winter Blends and Summer Blends

If you’re a red diesel user, or are thinking of switching to the rebated fuel, you need to know about the significant differences between summer and winter blends.

Red diesel, or gas oil, is for use in off-road vehicles, machinery, power and heating and must be manufactured to BS 2869 Class A2 standards.

If you’re a red diesel user, or are thinking of switching to the rebated fuel, you need to know about the significant differences between summer and winter blends.

What is red diesel?

Before we can explain the differences between winter and summer red diesel blends, it’s important to understand what red diesel is and how it’s used.

Red diesel is known by a number of different names including gas oil, tractor diesel, cherry red and 35-second oil, usually depending on which industry is using it.

If you’ve noticed the theme running through most of these names, there’s a reason for that – red diesel is dyed to signify that its sole use is in untaxed off-road vehicles, machinery, heating and power. The dye allows Customs & Excise to identify where it’s being used incorrectly.

Mixing red diesel with other petroleum products is strictly prohibited, and incorrect use can be punished by fines or criminal prosecution.

What are the different blends of red diesel?

There are two main blends or grades of diesel, widely referred to as summer and winter diesel.

Both have properties that make them suited to use in a range of applications, but they differ slightly in how they perform in extremely low temperatures.

Winter diesel has a lower viscosity and a greater resistance to gelling in low temperatures (-12oC CFPP min), making it better suited to use in the cold winter months.

In contrast, summer diesel’s higher viscosity makes it less resistant to gelling in cold temperatures (-4oC CFPP min), and sees far higher use in the warm summer months.

When can I buy winter fuel?

Fuel suppliers, like Nationwide Fuels, typically start supplying winter grade diesel from the 1st November and continue until the middle of March. This ensures that our customers receive the right fuel for the winter season, minimising downtime and the risk of fuel-related issues.

When can I buy summer fuel?

From the middle of March onward we switch back to supplying summer diesel as it’s able to function perfectly in the warmer conditions, with its limited (but still impressive!) resistance of up to -4oC.

Why not supply winter diesel year-round?

You could buy winter grade diesel all year but it simply wouldn’t be cost effective. During the refinement of crude oil far more summer grade diesel is produced, making it cheaper and more readily available than winter grade diesel.

When you take into account that summer grade diesel has higher energy content, the reasons for switching between grades becomes clear.

What happens if I use the wrong diesel grade in winter?

Machinery and equipment are more prone to operational problems in the winter months, especially those that are exposed to the elements.

Whether it’s difficulty starting or stopping the machinery, gearbox sticking issues or lubricant failure, the cause is usually the wrong grade of oils used.

With exposure to temperatures below their cloud point, poor thermal protection or microbial and physical contamination, fuel is most at risk from degradation in the winter.

What is the cloud point?

The cloud point of diesel is the temperature at which wax crystals begin to form within the fuel and are visible to the naked eye.

It’s a good indicator of the lowest temperature that it’s safe to store and use the diesel.

For example, summer diesel’s cloud point means that wax crystals start to form at -4oC, making that the lowest temperature that the fuel will function as intended. Winter grade diesel is safe to use for an additional eight degrees, having a cloud point of -12oC.

What is fuel contamination?

Whilst fuel contamination isn’t exclusively a summer or winter issue, it’s important to be aware of what it is and how it can affect your fuel.

Exposed or unprotected fuel tanks are at the mercy of the weather, leading to comparatively rapid fluctuations in temperature inside the tank. This can cause condensation to form inside the tank, creating a layer of water beneath the fuel where bacteria such as Diesel Bug can thrive.

Extreme conditions can also directly contaminate your fuel. With the rising risk of annual flooding across the UK, fuel tanks need to be more secure than ever to resist prolonged exposure to high water levels.

We offer a catalogue of fuel services to help preserve and prolong your fuel’s lifespan, from fuel testing, fuel polishing and fuel replacement to tank cleaning.

What causes fuel waxing?

Diesel is part of the paraffinic family of fuels, meaning that it contains wax paraffins.

Wax paraffins are an essential ingredient that give diesel its high cetane number, an indicator of efficient combustion. These paraffins are liquids that are dissolved in diesel and red diesel at normal temperatures.

When the temperature drops these paraffins begin to solidify, forming crystals that prevent the proper function of engines. They can block fuel filters, block pipework, prevent efficient combustion or even cause the engine to fail.

There are tell-tale signs to be aware of when looking for paraffin problems in fuel, namely:

  • The fuel will take on a milky, cloudy appearance
  • A red/brown deposit will form on the bottom of the tank and on the fuel filter
  • The engine will struggle to start, if at all

If your diesel is waxing, or if you think it’s in danger of waxing, you should replace it with the correct grade of fuel as soon as possible.

How can I protect my diesel?

Properly manage your fuel

Being aware of the diesel grade in your tank is key, especially when summer turns to winter. Try to run down your stocks of summer grade diesel in time to restock with winter grade as suppliers make the switch, or earlier if your supplier is able to meet your needs.

Don’t mix your grades

Mixing summer and winter grade fuels won’t give the resulting blend the best of both worlds. If anything, the cold resistance of your winter fuel will be compromised by the summer grade diesel, reducing its ability to resist colder temperatures.

Protect your tanks and engines

Protecting your tanks, pipework and engines is possibly the most straightforward and effective action you can take. Repairing or replacing thermal protection measures such as pipe insulation, or simply moving your tank to a more sheltered location can reduce your risk significantly.

Changing fuel filters as often as the manufacturer recommends is also important. They prevent any contaminants or wax crystals from entering your engines and causing expensive damage.

Get help from our fuel experts

Consider professional services such as our fuel management service or a priority fuel contract.

With these in place, you can be confident that your fuel is looked after year-round, with top ups of the correct fuel being delivered automatically and a dedicated account manager on hand to look after all of your fuel needs.

What lubricants should I use in winter?

Using the correct lubricants and greases is important year-round, but especially so in winter. The wrong oils can leave your engines and machinery dangerously exposed to high levels of friction and corrosion. You can minimise your risk in winter by checking the dipstick before starting any engines or machinery: if the lubricant or oil is lumpy or even solid, you know that it won’t perform as intended.

Where possible, you should follow your manufacturer’s recommendations when it comes to lubricants and oils.  At Nationwide Fuels, we can supply off-the-shelf industrial lubricants or even custom-blends that will meet your specifications exactly.

Can I use additives to protect my fuel?

Officially-approved and supplied additives can help improve the cold resistance of your red diesel. They are generally inexpensive and can dramatically improve your fuel’s condition.

It’s important to remember that additives won’t resolve issues that already exist within your fuel – such as dissolving paraffin crystals or removing contaminants. They are a preventative measure that modify paraffin crystals’ molecular structure, preventing them from growing too large. This is why they should only be added when the fuel is well above its cloud point.

Additives are already present in red diesel however; used by the manufacturer to ensure that the diesel they produce has the qualities that consumers need and that help control the fuel’s properties at high temperatures. These existing additives make it difficult to gauge how adding more might affect the fuel. Our fuel experts are on hand and can provide help and advice to ensure you get the best out of your fuel, simply call us on 0330 678 0880.

What are the cold properties of red diesel?

Red diesel’s cold flow specifications are measured by the cold filter plugging point (CFPP), with a specification of -12°C max in the winter and -4°C max in the summer (British Standard BS2869).

CFPP is measured under laboratory conditions using the EN 116 standard; a progressive cool-down procedure, specific pumping conditions and a filter mesh size of 45 microns. The EN 116 standard was developed by vehicle manufacturers in partnership with oil companies and is used to identify the cold resistance of current European gas oils.

The CFPP test shows a reliable correlation to engine performance and the test used across the EU for all grades of diesel to find the cold flow properties of the fuel.

The following is an excerpt from B2 2869, Section 8.2 – Seasonal Requirements

Gas Oil

Gas oil shall have the following maximum cold filter plugging point (CFPP) temperature in the given seasons.

For A2 and D fuels distributed from refineries and imported into the United Kingdom:

  • Summer: 16 March to 15 October inclusive, -4°C
  • Winter: 16 October to 15 March inclusive, -12°C

NOTE 1: The term “distribute” is as defined in the Motor Fuels (Composition and Content) Regulations 1999 (10)

For Class A2 and D fuels for delivery from terminals:

  • Summer: 16 March to 31 October inclusive, -4°C
  • Winter: 01 November to 15 March inclusive, -12°C

For class A2 and D fuels for delivery to end users, the seasonality dates are given in Table 1, Part 1 and Part 2 of this British Standard, i.e.:

  • Summer: 16 March to 15 November inclusive, -4°C
  • Winter: 16 November to 15 March inclusive, -12°C

What is Nationwide Fuels doing to minimise diesel issues?

Nationwide Fuels only ever supplies the best quality fuels and lubricants to its customers. We always take the season and customer’s location into account and supply only the most suitable products for that user’s individual needs.

We’re also doing our best to educate both our customers and the fuel-buying public by producing guides like this one, helping people to protect their own supplies.

Need to order red diesel today?

Now you know all you need to about the differences between winter and summer grade red diesel, we’re sure you’ll make the most of your fuel.

With truly nationwide coverage, quality products and same or next-day delivery available for quantities of 205-litres right up to 36,000 litres and more, you’re in safe hands with Nationwide Fuels.

If you have further questions about using red diesel in the summer or winter, you can speak to our fuel experts by giving us a call today on 0330 678 0880. You can also request a quote and place an order using the same number.

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