Gas Oil FAQ: What is Gas Oil and What Does it Do?

If you’re new to gas oil and interested in learning a little more about it, we’ve put together this gas oil FAQ to answer many of your questions about this type of fuel. As well as this FAQ, we also have a much larger red diesel FAQ that may well answer many more of your questions.

In case you’re not aware, red diesel is another of the more popular names for gas oil. Hopefully, our gas oil FAQ  (and of course our red diesel FAQ) will help answer many of the questions you may have about it such as; Is it illegal to use on the road? Is it the same as the regular diesel I buy at the pump? Can it be used all year round during the winter and the summer? And many other questions like these which we’ve answered for you.

As one of the UK’s leading gas oil experts, we’re here to help if you have any further questions about gas oil (or red diesel) and cannot find them in either of our FAQs. Or of course, if you have questions about making use of it within your business or how to purchase it. By all means, give our gas oil experts a call today on 0330 123 1144.

Common Gas Oil Questions

  1. What is gas oil?
  2. Does gas oil have any other names?
  3. Is gas oil the same as diesel?
  4. What colour is gas oil?
  5. What’s the difference between gas oil and heating oil?
  6. What is gas oil made from?
  7. What is gas oil used for?
  8. Has the specification of gas oil changed?
  9. Do you need a licence to buy gas oil?
  10. Can you mix gas oil with other fuels?
  11. Can gas oil be used all year round?
  12. What is marine gas oil?
  13. What is gas oil flash point?

What is gas oil?

Today, gas oil is mainly used as a commercial fuel in many industries for the purpose of powering machinery, generators and for vehicles used off-road, including those used in the agricultural, rail transport and marine sectors to name but a few.

It was also more commonly used by many businesses for heat generation, although in recent years, many businesses have now switched over to using industrial heating oil for heat generation instead. It can also sometimes be found being used in some domestic settings for heat generation too, but for most domestic users kerosene is now the heating oil of choice.

Does gas oil have any other names?

The name gas oil is one of the oldest names for this type of diesel and is still very popular today. However, the name red diesel has surpassed it in recent years, to the point where many people new to this type of fuel have never known it to be called anything but red diesel. The name quickly caught on due to the use of the red dye fuel markers which began to be added back in 1961.

The addition of the red dye was designed to help the authorities distinguish it from regular road diesel designated for use on public roads. Beyond gas oil and red diesel, you may have also heard it referred to as; tractor diesel, 35-second burning oil and plant fuel to name but a few. But they are all referring back to gas oil meaning marked diesel fuel designated for off-road use.

Is gas oil the same as diesel?

In simple terms, yes gas oil and regular diesel (DERV) are virtually the same fuel, except gas oil is strictly prohibited and is only to be used in off-road vehicles. The reason for this is because gas oil carries a much lower tax rate than the regular diesel that you buy at the petrol station. This makes gas oil a much more cost-effective alternative, as it doesn’t carry the same levies on tax as DERV.

For instance, fuels designated for use on public roads have a flat rate fuel duty of 57.95 pence per litre added to the price of the fuel, where as fuels meant for off-road usage have a very generous discount applied lowering their fuel duty to a flat rate of only 11.14 pence per litre.

The other difference is in the amount of VAT applied to the overall cost of the two fuels. Road diesel, like all road fuels, has the standard VAT rate of 20% applied to the cost of the fuel. Whereas sales of gas oil up to 2300 litres will only be liable for a 5% rate of VAT, with the full 20% VAT only being applicable for sales of gas oil over 2300 litres.

What colour is gas oil?

Gas oil contains a red dye that can be easily traced (hence the name red diesel) to help the police and DVSA identify illegal usage. Road diesel is not dyed, which is why it’s sometimes called white diesel.

If you’re found using red diesel in road vehicles, you could be subject to a hefty fine or prison sentence. You can learn more on the website

What is the difference between gas oil and heating oil?

Gas oil and heating oil (also commonly known as heating oil, paraffin, kero and 28-second oil) are both commonly used in commercial boiler applications. However, industrial heating oil (IHO) is a cheaper option than diesel for the same heat output as both of the fuels have the same calorific value.

What’s more, no modifications are required to your system if you change from diesel to IHO.

If you’re unsure about what vehicles and machinery can use diesel, please get in touch on 0330 123 1144. We can advise you on how you can use the fuel legally and save you money on your fuel costs too.

What is gas oil made from?

Gas oil is produced through a refining process where crude oil is pumped out of the ground to produce a thick, black liquid that’s known as petroleum.

Through the process of distillation, crude oil transforms into a variety of fuels, depending on the way it’s distilled. Crude Oil Fractionating

What is gas oil used for?

Some of the more popular uses of gas oil include:

  • Rail transport
  • Community amateur sports clubs and golf courses
  • Sailing, boating and marine transport (excluding private pleasure craft in Northern Ireland)
  • Travelling fairs and circuses
  • Fuel used for non-commercial purposes – electricity generation and heating
  • Agriculture, horticulture, fish farming and forestry

For more information, visit the HMRC website for more advice on using red diesel in vehicles.

Has the specification of gas oil changed?

Environmental legislation has necessitated cleaner fuels with less harmful emissions which have meant the British Standard for Gas Oil has had to change the specification to adhere.

Sulphur has been recognised as one of the most hazardous components in gas oil but was historically needed as a lubricant within the fuel.

This has led to a decrease in shelf life which means more regular fuel testing and analysis is needed to protect your assets and operations.

Do you need a licence to buy gas oil?

No, you don’t need a licence but you’ll need to sign an RDCO form.

What’s more, the company where you purchase gas oil must be registered with HMRC. It’s their responsibility to ensure that the fuel is being used legally.

They have a legal duty to pass on details of their transactions to HMRC which can be then used by the Road Fuel Testing Units (RFTU) if they suspect incorrect usage.

For more information, visit HMRC website.

Can you mix gas oil with other fuels?

You must never mix gas oil with other petroleum products as it’s illegal and could breach HMRC regulations in relation to payment for excise duty.

But there is one exception: industrial heating oil.

Red diesel can be directly topped up with IHO without having to empty the tank first.

Can gas oil be used all year round?

Gas oil has seasonal requirements that vary for both summer and winter use.

Winter-grade gas oil can be used all year round as it’s more resistant to cold (-12°C CFPP min). The blending of the fuel is altered during the colder months to improve performance.

Summer-grade gas oil is only suitable for use during the warmer months as it has limited resistance to the cold (-4°C CFPP). If you use summer-grade fuel in winter, you’ll experience operative problems such as engines failing to start.

What is marine gas oil?

Marine gas oil is a fuel used in seagoing vessels. ‘Bunker’ refers to a vessel’s fuel tank, which is why it’s often called bunker fuel too. Oil in the marine industry varies hugely, but here are the most popular nicknames it receives:

  • MDO – Marine diesel oil
  • IFO – Intermediate fuel oil
  • MGO – Marine gas oil
  • HFO – Heavy fuel oil
  • MFO – Marine fuel oil

What is gas oil’s flash point?

Firstly, let’s define what the flashpoint actually means:

  • The flashpoint refers to the lowest temperature at which it will produce enough vapour to cause a flammable mixture in the air
  • The lower the flashpoint temperature, the easier it is to ignite the air in the presence of an ignition source
  • The higher the flashpoint, the safer it is to handle
  • Diesel fuel flash points differ between 52 and 96 °C (126 and 205 °F)

Need more information? You can find more information on our red diesel FAQ, or alternatively, get in touch with our knowledgeable fuel experts who can answer any other questions you may have about gas oil/red diesel.

If you have any questions about gas oil, or if you’re looking for a competitive gas oil quote, get in touch with our gas oil experts today on 0330 123 1144.

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