What is gas oil? In short, it’s a diesel-type fuel most people in the UK know as red diesel. It runs eligible farm machinery and certain other engines, and it’s also used in some heating systems and generators. It’s very close to the diesel you put in a van, but the rules on who can use it, and what for, are very different.
Stoddards has supplied local homes, farms and businesses since 1966, delivering across Staffordshire and parts of Cheshire, Shropshire and Derbyshire. This guide explains what gas oil is, what it’s used for, the specification we supply, how it compares with DERV and kerosene, and the basics of who can use it.
What Is Gas Oil?
Gas oil is a middle-distillate fuel refined from crude oil, from the same family as road diesel. In everyday UK fuel supply, the term usually means red diesel, diesel that’s dyed red and chemically marked so it can be sold at a lower, rebated rate of duty for permitted uses only.
You’ll hear it called by several other names, and they all point to the same product:
- Red diesel
- Marked gas oil
- Farm diesel or tractor diesel
- 35-second oil
The “35-second” name comes from a traditional viscosity test, which is how the trade has long told heavier gas oil apart from lighter “28-second” kerosene.
Is Gas Oil the Same as Red Diesel?
In practice, yes. When a fuel supplier talks about gas oil, they almost always mean red diesel. Strictly speaking, though, “gas oil” describes a type of fuel, whilst “red diesel” describes gas oil that’s been dyed and marked for rebated-duty use.
The red dye and chemical markers are there so HMRC can identify the fuel and check it’s being used lawfully. HMRC officers have the power to sample fuel from vehicles, machines and storage tanks, and HMRC’s own guidance, Excise Notice 75, uses red diesel, marked diesel and marked gas oil as names for the same rebated fuel.
What Is Gas Oil Used For?
Gas oil is used to run diesel engines and fuel heating equipment wherever the law allows a rebated fuel. Today, the main users are farms and growers, forestry, the rail industry, boats and ships, and people heating or powering non-commercial buildings such as homes, places of worship and village halls.
Farm vehicles and machinery
Agriculture is the biggest use of gas oil across our area. Tractors, combine harvesters, crop sprayers and other agricultural vehicles can run on it when they’re being used for farming work, along with machines such as grain dryers, farm generators and pumps. Horticulture, aquatic farming and forestry are covered in the same way. Our agricultural fuel service is set up for exactly this kind of supply.
It’s the job that counts, not just the machine. A digger used for drainage work on farmland can qualify, but the same digger working on a housing development can’t.
Heating homes and other non-commercial buildings
Gas oil can be used for heating and electricity in premises that aren’t used for commercial purposes. That includes homes, places of worship, state schools, NHS hospitals and town halls. HMRC treats an appliance as serving non-commercial premises if at least 75% of the heat or power it produces goes there.
Some older domestic heating installations were designed to run on gas oil, so you may still find it in rural homes. Most modern domestic boilers, though, are built for kerosene. If you’re a domestic customer and you’re not sure which fuel your boiler takes, check with your heating engineer or give us a call.
Rail, boats and other permitted uses
A handful of other uses still qualify, including:
- Locomotives and rail maintenance vehicles
- Boats and ships, apart from private pleasure craft (pleasure boat owners in Great Britain can fill up with red diesel but must declare what they’ll use for propulsion and pay full duty on it)
- Machinery used on golf courses and community amateur sports club grounds
- Travelling fairs and circuses
- Tree work machinery such as woodchippers and stump grinders
Uses that no longer qualify
Since April 2022, most construction plant, commercial standby generators and gas oil heating for commercial premises no longer qualify. Interestingly, the rules are different for kerosene. A kerosene heating system can use rebated fuel to heat any premises, including commercial ones. That’s worth knowing if you run a business and are reviewing how you heat your site.
What Specification Is Stoddards’ Gas Oil?
The red diesel we supply is made to BS EN 590, the same standard as our white road diesel (DERV). The only differences are the red dye and statutory markers, the lower rate of duty, and the restrictions on who can use it and for what purpose.
Our supplied specification includes:
- A minimum cetane number of 51
- A maximum sulphur content of 10 parts per million
- Up to 7% FAME, the biodiesel component used in conventional diesel blends
Not all gas oil on the market is supplied to the same standard. Some is sold to a different British Standard, BS 2869, which sets different requirements. Whoever you buy from, it’s worth checking the supplied specification against your equipment manufacturer’s requirements, particularly for newer machinery.
Gas Oil vs DERV: What’s the Difference?
DERV is white diesel with full duty paid, and it can be used in any diesel road vehicle. Our gas oil is the same BS EN 590 fuel, dyed red and marked, sold at a rebated rate of duty and restricted to permitted uses. Same fuel quality, different tax and different rules.
| Gas oil (red diesel) | DERV (white diesel) | |
|---|---|---|
| Specification (Stoddards) | BS EN 590 | BS EN 590 |
| Colour | Dyed red, chemically marked | Undyed |
| Fuel duty | Rebated (lower) rate | Full rate |
| VAT | 5% or 20%, depending on use and quantity | 20% |
| Who can use it | Qualifying vehicles, machines and uses only | Anyone, including road vehicles |
For more on road diesel, read our guide to what DERV is.
Gas Oil vs Kerosene, What’s the Difference?
Kerosene, or 28-second oil, is a lighter, thinner heating fuel used in most domestic oil boilers and some oil-fired cookers. Gas oil, or 35-second oil, is heavier and is used in diesel engines and heating equipment designed for it. The two aren’t interchangeable, so always check what your appliance needs.
Our heating kerosene meets BS 2869 Class C2. Because some older domestic installations still run on gas oil, the right choice depends entirely on your appliance, and you shouldn’t swap one for the other without checking the manufacturer’s requirements. Our guide to what kerosene is covers the domestic heating side in more detail.
Who Can Use Gas Oil?
Since 1 April 2022, gas oil can only be used in specified vehicles, machines and appliances, and only when they’re being used for a qualifying purpose. Being off-road isn’t enough on its own. It’s the combination of the machine and the job that decides whether red diesel is allowed.
For example, a generator doesn’t qualify just because it sits on private land, and a digger doesn’t qualify just because it never goes on the road. Our full guide to who can use red diesel goes through the eligible uses sector by sector. If you’re still unsure, speak to our team before you order.
Can gas oil be used on public roads?
Not in ordinary road-going cars, vans or lorries. However, eligible agricultural vehicles can use red diesel on public roads when they’re being used for a qualifying purpose, such as a tractor travelling to a field to carry out farm work.
That doesn’t mean every tractor journey qualifies. The deciding factors are the vehicle and the activity, not simply whether it’s on or off the road.
What happens if gas oil is misused?
Using red diesel where it isn’t allowed is treated seriously. HMRC can seize the vehicle or machine, recover the duty owed going back up to four years, and add a penalty. In the most serious cases, offenders can face an unlimited fine or up to seven years in prison.
How Much Duty and VAT Is on Gas Oil?
Gas oil carries a much lower, rebated rate of fuel duty than road diesel, which is the main reason it costs less. Eligible deliveries of up to 2,300 litres generally attract 5% VAT. Larger supplies for business use normally attract 20%, although some domestic and charity uses still qualify for 5%.
Fuel duty on gas oil
As of October 2026, the rebated rate on gas oil is 6.48p per litre, temporarily cut from 10.18p until 31 December 2026. Standard road diesel is 52.95p per litre. Both rates are due to rise from 1 January 2027, with the final figures to be confirmed at the Autumn Budget. [Source: HMRC, Amended Fuel Duty rates: 2026 to 2027]
Duty rates change at fiscal events, so always check the current figure rather than relying on an old one. You’ll find the latest position in our guide to the [PLACEHOLDER: link to red diesel price article, anchor “price of red diesel”].
VAT on gas oil
Under HMRC’s small-quantity rules, eligible gas oil deliveries of up to 2,300 litres generally attract the reduced 5% rate. Larger supplies for business use normally attract the standard 20% rate, but qualifying domestic and charity non-business use can still be charged at 5%.
HMRC generally treats deliveries to the same site on the same day as one supply when applying the 2,300-litre threshold. You can read the detail in VAT Notice 701/19: fuel and power, or ask us and we’ll explain the VAT treatment that applies to your order.
Gas Oil FAQs
Is tractor diesel the same as gas oil?
Yes. Tractor diesel, farm diesel and red diesel are all everyday names for gas oil that’s been marked for rebated-duty use. The name you hear usually depends on who you’re talking to, but the fuel is the same.
Can I heat my home with gas oil?
Yes, homes count as non-commercial premises, so gas oil can legally be used for domestic heating. The bigger question is whether your boiler is designed for it. Most modern domestic boilers run on kerosene, so check with your heating engineer before ordering.
Can I put gas oil in my car or van?
No. Ordinary road vehicles must run on fully duty-paid white diesel. Putting red diesel in a car or van, even briefly, can lead to the vehicle being seized and a penalty.
Can I run a generator on gas oil?
Only in certain cases. A generator can use red diesel if it’s mainly powering non-commercial premises, such as a home, or if it’s being used for agriculture or another qualifying purpose. Most commercial standby generators no longer qualify.
Is gas oil the same quality as road diesel?
Ours is. The red diesel we supply is made to BS EN 590, the same standard as our DERV. Other suppliers may use a different specification, so it’s always worth asking.
Order Gas Oil from Stoddards
We supply BS EN 590 red diesel to eligible farms, homes and businesses across Staffordshire and parts of Cheshire, Shropshire and Derbyshire, alongside white diesel (DERV) and heating kerosene. Whether you need fuel for agricultural machinery, a qualifying generator or another permitted use, we can help you choose the right product and arrange delivery.
Explore our red diesel and gas oil delivery options, or contact our team for a quote and advice on your requirements.