With older diesel cars about to face a £10 a day congestion charge for “polluting” London, it’s no longer clear cut as to which is a better investment.  We take a look at whether it is better to buy a petrol or diesel car.  Petrol vs Diesel – who wins?

Initial Purchase Cost

Based on the cost of a brand new car – petrol cars win.  Diesel cars cost around £1000 – £2000 more than a brand new petrol car.

Secondhand Market

Once again, a petrol car is a cheaper purchase.  Diesel cars retain a higher resale value whereas the petrol cars depreciate quicker making them more suited to the secondhand car market.

Fuel economy

Diesel costs more per litre than petrol (around £3.30 more if you are filling up a 50 litre tank) but you get more for your mileage, ie you can drive 25% further in a diesel-powered car than you can with a petrol one.


A diesel car service will generally set you back more than if you had a petrol car serviced however diesels don’t need to be maintained as routinely as petrol cars.

Car Insurance

Petrol cars are cheaper to insure.  Insurance can be 10 – 15% higher on diesel cars due to the higher accident repair costs.  Also as diesel cars are more expensive to buy new (and they retain their value more), the overall replacement cost is higher.

Others Factors To Consider

Road tax – diesel car owners pay less road tax as they produce less CO2 emissions

Small cars – smaller cars tend to be petrol because they are cheaper to produce and adding a diesel engine would bump up the price too much

Which drives better? Diesel-powered cars were traditionally noisy vehicles but that is no longer the case, also you can change gear at lower revs

DPF (the diesel particulate filter) – These aren’t cheap to replace (between £1000 – £2000!) but as all new diesel cars are fitted with them, it means you don’t release as much CO2 thus you pay less road tax. Look at the type of driving you are doing – if you are stop/starting and driving around town they will tend to get blocked more than if you are covering long distances.


Based on all the factors above, we think that a brand new diesel purchase is great if you are travelling long distances but if you want a car just to run about town then you may wish to consider a petrol car as an option.  However, if you are still undecided, try using Which? Driver tools – Petrol vs Diesel calculator

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