Kerosene vs. Gas Oil: What is the Difference?
Not All Heating Oil Is the Same
If you're new to oil heating, you might be confused by the different terms thrown around: Kerosene, Gas Oil, Red Diesel, 28-second oil, 35-second oil. Are they interchangeable? (Short answer: No!)
Using the wrong fuel can damage your boiler, void your warranty, and even be illegal. Here is the definitive guide to the differences.
1. Kerosene (28-Second Oil)
Also known as: Regular Heating Oil, Burning Oil, Standard Kero, 28-Second Oil.
Appearance: Translucent yellow (like white wine) or clear.
Usage: This is the standard fuel for home heating in the UK. Virtually all modern domestic oil boilers (and AGAs) are designed to run on Kerosene.
- Why "28-second"? This refers to its viscosity (thickness). It takes 28 seconds for a specific amount of this oil to pass through a standard test orifice. It is lighter and cleaner-burning than gas oil.
- Clean Burning: It produces less smoke and soot, making it more efficient and kinder to your boiler's internal parts.
- Anti-Freeze: While Kerosene has a low freezing point, it can wax in extreme cold. If your tank is very exposed, you might use "Premium Kerosene" which contains additives to prevent this.
2. Gas Oil (35-Second Oil / Red Diesel)
Also known as: Red Diesel, Tractor Diesel, Cherry, 35-Second Oil.
Appearance: Dyed bright red.
Usage: Gas Oil is effectively diesel fuel (like you put in a car) but with a red dye to indicate it has a lower tax rate for agricultural/industrial use. It is illegal to use in road vehicles.
- Commercial/Agricultural: It is primarily used for tractors, farm machinery, generators, and some older, large commercial heating systems.
- Heavier: It is "thicker" (35-second viscosity) and burns "dirtier" than Kerosene.
- Regulation Changes: As of April 2022, the UK government significantly restricted who can use Red Diesel to try and improve air quality. Most commercial heating contracts have had to switch to Kerosene or other alternatives.
Can I Mix Them?
Strictly, No.
- Putting Gas Oil in a Kerosene Boiler: The thicker fuel will clog the nozzle and soot up the heat exchanger very quickly. It may not ignite at all.
- Putting Kerosene in a Tractor/Generator: Kerosene lacks the lubricating properties of diesel. Running an engine on Kerosene will rapidly destroy the fuel pump and injectors.
What Is "Premium" Kerosene?
You might see suppliers offering Premium Kerosene (e.g., Kero+, Exocet). This is standard 28-second Kerosene that has been pre-dosed with additives.
Benefits usually include:
- Fragrance: Reduced smell.
- Efficiency: Clean-burn agents to reduce soot.
- Stability: Antioxidants to keep the fuel fresh longer in the tank.
- Cookers: Special variants exist for AGAs/Rayburns which are cleaner burning to prevent "sooting up" the cooker.
Summary Table
| Feature | Kerosene (Standard Home Oil) | Gas Oil (Red Diesel) |
|---|---|---|
| Viscosity | 28 Seconds (Runnier) | 35 Seconds (Thicker) |
| Colour | Yellow / Clear | Red |
| Primary Use | Home Heating / AGAs | Tractors / Generators |
| Soot Levels | Low | High |
| Tax Rate | 5% VAT (Domestic) | Varied (Commercial) |
The Takeaway: If you are a homeowner, you almost certainly need Kerosene (28-second oil). Always double-check your order to ensure you aren't buying the wrong fuel type.
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