If you drive a diesel car in the UK, the fuel you put in is almost always "B7". The label appears on every diesel pump, but few drivers know what it means. Here's a plain-English guide.
What B7 actually means
Just as petrol's "E" stands for ethanol, diesel's "B" stands for biodiesel — specifically FAME (fatty acid methyl ester), a renewable fuel made from vegetable oils and fats. The number is the maximum percentage blended in:
- B7 contains up to 7% biodiesel mixed with regular mineral diesel. It is the standard diesel sold at virtually every UK forecourt.
- B10 (up to 10% biodiesel) exists in some European markets but is not the UK standard.
The black-and-white "B7" square you see on the pump and inside many fuel filler flaps is part of an EU-wide fuel labelling scheme designed to help drivers match the right fuel to their vehicle across different countries.
Standard vs premium diesel
Alongside standard B7, most major forecourts sell a "premium" or "super" diesel at a higher price. These premium diesels are still B7 at heart, but include extra additives intended to clean injectors, reduce deposits and improve performance over time. For most drivers, standard B7 is perfectly fine and the cheaper choice; premium diesel may benefit older or high-mileage engines, but the everyday savings of standard B7 usually win.
Where HVO fits in
You may also see HVO (hydrotreated vegetable oil), sometimes called renewable diesel. HVO is a cleaner-burning, fully renewable diesel substitute that can dramatically cut lifecycle carbon emissions. It's increasingly used by fleets and is starting to appear at a small number of public forecourts, but it remains far less common — and usually more expensive — than standard B7. Not every diesel engine is approved for HVO, so check your manufacturer's guidance before using it.
Can all diesel cars use B7?
Yes. Every diesel vehicle sold in the UK is designed to run on standard B7, so you never need to worry about compatibility at an ordinary forecourt — unlike the E10 petrol situation, where some older cars are excluded. The only time you need to check is if you plan to use a higher biodiesel blend or HVO.
Saving money on diesel
Because all UK forecourts sell the same standard B7, the main way to cut your diesel costs is simply to find the cheapest pump near you. Supermarket forecourts usually undercut branded stations, and motorway services are typically the most expensive. Prices between two stations a few miles apart can differ by 10p a litre or more.