When it comes to powering machinery, heating buildings, or keeping essential operations running smoothly, gas oil remains one of the most widely used fuels across the United Kingdom. Often referred to as red diesel, gas oil has played an essential role in agriculture, construction, manufacturing, and off-road transport for decades. Yet, despite its widespread use, many businesses and consumers still misunderstand what gas oil truly is, how it works, and how current regulations affect its usage.

With over twenty years of experience writing about fuel markets, energy trends, and UK industry practices, I’ve created this comprehensive guide to help you understand gas oil from every angle—what it is, how it’s used, the legal requirements, and what to consider when buying it.

What Is Gas Oil?

Gas oil is a low-tax fuel primarily intended for off-road engines and commercial heating applications. Chemically, it is similar to road diesel but contains a red dye and chemical markers that identify it for regulated use. This dye is crucial because it prevents tax evasion—gas oil enjoys a significantly lower duty rate compared to standard white diesel used on public highways.

In simple terms:

  • White diesel = road use

  • Red diesel (gas oil) = off-road and heating use

This distinction is vital for businesses in the UK to remain legally compliant.

Where Gas Oil Is Commonly Used in the UK

Gas oil remains essential across a range of UK industries, especially those reliant on heavy machinery or high-capacity heating systems. Some of the most common uses include:

1. Agriculture

Farmers use gas oil for tractors, harvesters, loaders, and backup generators. Its reduced tax makes it an affordable option for essential food production machinery.

2. Construction and Civil Engineering

Excavators, cranes, dumpers, telehandlers, and mobile compressors historically ran on gas oil. However, 2022 reforms significantly restricted this usage—more on that shortly.

3. Industrial and Commercial Heating

Large commercial buildings, factories, warehousing spaces, and greenhouses often rely on gas oil for cost-effective heating.

4. Marine and Offshore

Many inland boats, barges, and fishing vessels use gas oil as a practical fuel for engines and onboard heating.

5. Rail Transport

Railway maintenance vehicles and some locomotives may operate on gas oil, especially on non-electrified lines.

Understanding these applications helps businesses choose the correct fuel while avoiding compliance issues.

Gas Oil vs Diesel: What’s the Difference?

Although gas oil and white diesel share many characteristics, the differences matter when it comes to taxation, engine performance, and legal usage.

Key Differences:

  • Colouring & Chemical Markers:
    Gas oil is dyed red and includes government-approved markers to identify misuse.

  • Tax Rate:
    Gas oil is taxed far lower than white diesel, making it cheaper but tightly regulated.

  • Intended Use:
    White diesel is the only legal option for road vehicles.
    Gas oil is restricted to specific industries and applications defined by UK law.

  • Performance:
    For most modern engines designed to accept off-road diesel, performance differences are minimal. However, incorrect use in road vehicles can damage emissions systems and result in severe penalties.

Red Diesel Rule Changes in the UK: What You Must Know

A major turning point came in April 2022, when the UK government significantly reduced the number of industries allowed to use gas oil. This reform aimed to encourage cleaner energy adoption and cut carbon emissions.

Industries and Applications That Can Still Use Gas Oil:

  • Agriculture and horticulture

  • Non-commercial boating

  • Rail transport

  • Certain heating applications

  • Off-grid electricity generation in specific scenarios

Industries That LOST Eligibility:

  • Construction

  • Logistics and material handling

  • Outdoor events and festivals

  • Highway maintenance

  • Commercial refrigeration units on lorries

If your business no longer qualifies but continues using gas oil, the penalties can be severe—including heavy fines and possible equipment seizure. Staying updated on the law is essential.

Benefits of Gas Oil

Despite the tightening regulations, gas oil remains highly valuable for those who are still permitted to use it. Benefits include:

1. Cost-Effective Fuel

Its lower tax rate makes it cheaper than standard diesel, reducing operational expenses dramatically.

2. Efficient Heating

Gas oil burns hotter and more steadily than some alternative fuels, making it ideal for commercial heating systems.

3. Versatile Applications

From farm machinery to marine engines, gas oil works across a variety of heavy-duty applications.

4. Reliable for Backup Power

Businesses using gas oil-powered generators benefit from dependable power during outages or peak demand.

How to Store Gas Oil Safely in the UK

Proper storage ensures fuel quality, reduces safety risks, and keeps you compliant with UK environmental regulations.

Best Practices for Storage:

  • Use an approved fuel storage tank made of steel or high-quality plastic.

  • Keep the tank in a bunded enclosure to prevent spills.

  • Protect tanks from frost, condensation, and contamination.

  • Regularly test and treat fuel to prevent bacterial growth.

  • Label storage containers clearly as gas oil/red diesel.

Compliance with OFTEC and UK environmental guidelines is crucial.

Tips for Buying Gas Oil in the UK

When choosing a supplier, consider the following:

1. Delivery Speed

Rural areas, farms, and construction sites often need urgent delivery. Opt for suppliers offering same-day or next-day service.

2. Seasonal Pricing

Fuel prices fluctuate. Ordering during off-peak periods—often spring or early summer—can reduce long-term costs.

3. Fuel Quality

Premium-grade gas oil contains additives that improve engine cleanliness, reduce emissions, and enhance winter performance.

4. Local vs National Suppliers

While national suppliers offer competitive rates, local companies may provide faster support and personalised service.

The Future of Gas Oil in the UK

As the UK transitions toward greener energy, long-term dependency on gas oil is expected to decline. Hydrogen, HVO (hydrotreated vegetable oil), and electrification are some of the emerging alternatives. However, for many sectors—particularly agriculture and marine—gas oil will remain a critical fuel for years to come.

The shift will be gradual, and businesses should stay informed to plan ahead responsibly.

Final Thoughts

Gas oil continues to be an essential fuel across many UK industries, despite evolving regulations and increased pressure toward sustainable alternatives. Understanding what gas oil is, how it works, who can legally use it, and how to buy and store it effectively ensures businesses remain compliant and efficient.

Whether you're managing farmland machinery, heating a commercial building, or running off-grid equipment, gas oil remains a cost-effective and dependable solution—as long as it’s used correctly.