Question of the week: Should I buy a diesel car in 2025?

Matt Robinson, Car Reviews Editor
Fri, 04 Jul 2025

Dear Honest John,

"I'm looking to buy a car this year. Should I avoid buying a diesel car now? Do they still make sense?"

- DE

Dear DE,

It would depend on the kind of mileage you’re doing. For anyone clocking significant mileage, diesel still makes a lot of sense. 

While petrol cars have been getting more and more economical over the years, they still can’t compete in terms of miles per gallon, while plug-in hybrids only make sense if you’re completing a lot of smaller journeys that can be covered on electricity added by charging at home. 

If you’re buying a diesel car registered after 1 April 2017, you’ll pay no more tax than a petrol, hybrid or electric vehicle, with all now liable for the same £195 annual rate. Meanwhile, although diesel is priced higher than petrol, the difference has narrowed, with the gap being around 7p per litre on average. 

If you’re buying a little older, you will need to bear in mind that only diesel cars that comply with Euro6 emissions regulations, which are those registered after September 2015, will be compliant with the UK’s various Ultra Low Emission Zones (ULEZ). Petrol cars only need to be Euro4, which applies to vehicles registered in 2005 and later. 

Euro6 diesel cars also require AdBlue, filled in a separate tank, the size of which can vary. On a BMW 320d, for example, it’s around 12 litres.

A full tank of AdBlue will last anything from around 3000 miles to over 10,000. The car will warn you well in advance if it’s getting low, and AdBlue is easy to get hold of. Most petrol stations sell it and the cost ranges from about £10 to £15 for 10 litres.

Ask HJ

What's best to buy now - diesel, petrol or hybrid?

We've always bought diesel cars as they do many miles, good MPG etc. We are looking at replacing our car - what's best to buy now diesel, petrol or hybrid? We don't want an electric - they just do enough miles for us in one go.

Thanks for your question. If you're regularly clocking a lot of miles, diesel does still make perfect sense, even though it's now a little 'out of fashion'. We'd only recommend a plug-in hybrid if you're able to charge from home via a 'wall box' and make the most of the electric-only range. Petrol and 'self-charging hybrid' cars can be very economical as well, so are worth considering depending on the sort of annual mileage you do.

Answered by Matt Robinson

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