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

Learn more about gas oil, who uses it and if it could benefit your business

No matter whether you’re new to gas oil and looking to learn more about it or have been using it for many years and simply curious to learn more. We’ve put together a short guide to help you get up to speed with gas oil.

You can also call and discuss your requirements with our gas oil experts, by calling us today on 0330 123 5665.

What is gas oil and is it known by any other names?

Gas oil is known by a few names, but one of the more popular names is red diesel due to the red dye marker that was added to gas oil from the 1960s to help authorities to quickly check if a vehicle was being run on gas oil.

The reason for this is because red diesel and white diesel (also known as road diesel or just diesel) are essentially the same fuel, but taxed very differently. The white diesel you see available from petrol stations throughout the UK is taxed at a far higher rate in line with petrol, whereas red diesel (gas oil) has a far lower fuel duty applied to it.

This makes it very tempting for many diesel vehicle owners looking to save money, to buy and use it in their vehicles. However, it is illegal to use gas oil on public roads, hence the need to use the red dye markers in order to spot any illegal use on public roads.

You may have noticed and wondered if gas oil had anything to do with the fuel known simply as “gas” in America or maybe “natural gas” which is used to heat homes and business in the UK. In short, they’re all different products, so lets start with the latter two products first and then we’ll get back to gas oil.

Gas / Gasoline (USA)

It’s easy to see where some people may become confused and assume that when Americans talk about filling their vehicles with gas, they’re talking about using gas oil.

However, gas is simply a shorthand way of saying and writing gasoline, in the same way as we in the UK have shortened petroleum to petrol. They’re simply two (or rather four) names for the same product, so nothing to do with gas oil.

Gas / Natural Gas / Fossil Gas (UK)

Although you will quickly realise now that natural gas which the majority of businesses and homes know well for piping heating and cooking fuel into our homes and businesses. Isn’t technically anything like the liquid fuel known as gas oil.

Gas Oil / Red Diesel

Gas oil was originally used for heating homes and businesses before natural gas become more prevalent. But as time went on and motor vehicles became more widespread, gas oil also became a popular fuel for use in many vehicles in the early part of the 20th century.

Although the government introduce fuel duty on fuels intended for use in road vehicles in 1928. There was a rebate for gas oil which had existed in one form or another between 1928 and 1935 because gas oil was still mainly used for heating at the time.

By 1935 due the widespread use of diesel engine road vehicles, the government withdrew the rebate for use in road vehicles, leaving it in place for all other uses including heating and for those vehicles that were already paying the lower rate of vehicle excise duty (VED) such as tractors and other agricultural machines, which became known as “excepted vehicles” that would only be used on public roads occasionally, so were not considered to be “road vehicles”.

It wasn’t until 1961 that a red dye marker was added to gas oil, leading to the nickname “red diesel”, a name which has slowly grown in popularity with the majority of people these days knowing it as red diesel rather than gas oil.

How is gas oil made and where does it come from?

Gas oil comes from crude oil, the crude oil that is pumped out of the ground is a black liquid, known as petroleum. Depending on the way that the crude oil is distilled, a variety of fuels can be made.

The illustration below shows a more detailed view of how gas oil and other fuels are distilled from crude oil.

how gas oil is made from crude oil

Which industries use gas oil?

Of course, there are many industries that use gas oil within their off-road vehicles and also in generators and other machinery. But to give you some idea about specific industries, we’ve listed a few of them below to give you greater insight into who uses it and where they use it.

Agricultural industry

One of the main users is the agricultural industry who use gas oil. With farmers using many different machines and vehicles on a farm, these will mostly be powered by gas oil. But don’t think it’s used to fuel just tractors and combine harvesters; farmers have grain dryers and heaters that need powering too.

Construction industry

Another common sector that uses gas oil is the construction sector, with excavators, generators, cranes, dumper trucks and lots of other machines & vehicles. The sheer number of uses in construction gives you an idea of how much fuel the typical construction site will use.

Smelting industry

Another sector which you might not normally think of is the smelting industry. They use gas oil to power their furnaces which melt the metals. These need lots of fuel to get the heat up to the required temperatures.


One more sector which doesn’t usually spring to mind is data centres who use gas oil to power generators. These need fuel for their backup generators in case they have a power failure and want to avoid hard drives and computers shutting down. In this instance, gas oil is absolutely essential for a smooth running of services.

Further information and gas oil quotes

Hopefully, the information on this page has answered many of the questions you may have had about gas oil. We have further information about gas oil (red diesel) in our FAQ.

If you would like to learn more and discuss your requirements with one of knowledgeable team, give us a call on 0330 123 5665 today. You can also request a quote based on your own gas oil requirements.