Fuel Types & Quality Petrol vs Diesel

Is my car petrol or diesel?

Q: Is my car petrol or diesel?

Check the sticker inside your fuel filler flap — it will state the fuel type or show a nozzle symbol. A circle symbol means petrol; a square means diesel. You can also check your V5C logbook under section D, or use the free DVLA vehicle enquiry service at GOV.UK with your registration plate.

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The quickest way to find out if your car is petrol or diesel is to check the fuel filler cap or the sticker inside the fuel filler flap — it will say 'petrol', 'diesel', or show the correct nozzle symbol. If that is unclear, your V5C registration document (logbook) lists the fuel type under section D.

Check the Fuel Filler Cap and Flap

Filler flap sticker: Most cars made after 2000 have a label inside the fuel filler flap stating the correct fuel type. It may also show a green cap for petrol (E5/E10) or a black cap for diesel. 2

Nozzle size symbols: Since 2018, EU and UK regulations require fuel nozzle symbols on the filler flap — a circle indicates petrol, a square indicates diesel. 2

E10 label: If you see 'E10' or 'E5' marked on the filler flap or cap, your car takes petrol. E10 is the standard unleaded petrol sold at most UK forecourts. 3

Check Your V5C or Owner's Manual

V5C logbook: Your V5C registration certificate lists the fuel type in section D. If you do not have a V5C, the DVLA holds this information and it is also shown on the MOT certificate.

Owner's manual: The owner's manual always states the correct fuel grade and type on the opening pages or in the technical specifications section.

DVLA vehicle enquiry: You can confirm your car's fuel type for free using the DVLA's online vehicle enquiry service at GOV.UK — you just need the registration plate. 2

Other Ways to Tell the Difference

Engine sound: Diesel engines are typically louder and produce a rattling or clattering sound at idle compared to the smoother, quieter sound of a petrol engine.

Filler nozzle size: Diesel pump nozzles are physically wider than petrol nozzles, so a diesel nozzle will not fit easily into a petrol car's filler neck — a safety measure to prevent misfuelling. 2

Fuel economy and use case: Diesel cars typically achieve higher MPG on longer motorway journeys, while petrol suits shorter urban trips. Which? data shows diesel usually only saves money if you cover 10,000+ motorway miles per year. 4

Why Getting It Right Matters

Misfuelling is costly: Putting diesel into a petrol car, or petrol into a diesel car, can cause serious engine damage. Never guess — always confirm before you fill up.

Find the right fuel price: Once you know your fuel type, use CheckFuelPrices to compare live petrol or diesel prices at stations near you, updated every 30 minutes from CMA government data. 1