Is it worth getting a new diesel car?

Published Date: 30th Jul 2015

This is the question that runs through the mind of every UK buyer, when looking for a new car. In this article we will look through all the benefits and the drawbacks of spending you hard-earned cash on a new Diesel car.

Current Price of Diesel Fuel

We will start with the current price of diesel fuel, which we have seen drop in the last month or so to below the price of petrol for the 1st time in 15 years. This is the first time this has ever happened. Supermarkets are leading the way; with Tesco, Sainsbury’s and Morrison’s all reducing diesel twice in the last few weeks. The established petrol stations; Shell, BP and Texaco took a little longer to catch on.  

The RAC announced last week that throughout the whole of June, the wholesale price of diesel was between 1p to 3p cheaper than petrol, yet a litre of diesel typically costs motorists 120p compared to 117p for unleaded.

Simon Williams, RAC fuel spokesman, explained: 'The RAC campaigns for retailers to sell fuel at a fair price to motorists.

'While pricing at the pumps is ultimately in the retailer's hands, it is disappointing that some choose to effectively subsidise the lower cost of diesel by increasing the price of unleaded.

'The fact is that the wholesale price of petrol has also been falling, albeit to a lesser extent than diesel. So at the very least unleaded pump prices should be static at forecourts, if not coming down by 1p.'


Luke Bosdet, AA spokesman, said that while supermarkets are leading the charge, those who do not live near one face higher diesel costs.

He explained: 'Many of the supermarkets can be applauded for recent price cuts but it is what is happening outside the areas they influence that worries us.

'Yesterday, diesel at motorway service areas cost as much as 127.9p a litre while petrol cost 125.9p.

'This compares with an average of around 116.6p / 116.7p a litre across the UK. The message is clear to diesel drivers - check out the supermarket prices first if they are looking to cut their fuel bills.'

He added: 'Diesel drivers will think that the latest fall in the cost of their fuel is "better late than never" and is very welcome.

'However, the average pump price of diesel across the UK remains above petrol's even though the former is around 3p a litre cheaper at wholesale level.'

Simon Williams then added: 'Filling stations further away from supermarkets may well charge differently as pricing is often determined by local retail dynamics.

'When there isn't a supermarket or an independent retailer nearby that likes to compete on price, higher prices are very often the result.

'Retailers are, of course, free to charge what they want for the fuel they sell, and while that is based on wholesale prices they can choose to charge more for one fuel than the other if they think it suits their customers.

'As a result not every motorist in the country is yet to benefit from the fall in the diesel wholesale price – the average price of diesel sold at the pumps is still higher than petrol, despite diesel being bought in by retailers for less than the price of unleaded since the end of May.

'We expect the diesel/petrol average price "flip" to occur in the coming days, and when it does there will be huge pressure on all retailers in the UK to sell diesel for less than petrol, reflecting more closely the wholesale price.'

Diesel Particulate Filter

Around 50 percent of the vehicles on UK roads are diesel which comes as no surprise, as many drivers look to save money on their fuel costs. But there is more to take into consideration - Cars today have to a dear to emission regulations and to do that, car-makers are fitting diesels with diesel particulate filters to reduce the emissions from the exhaust system.


Does the Diesel Particular Filter (DPF) affect fuel efficiency (MPG)

The diesel particulate filter (DPF) is just safety net that catches the harmful emissions, especially when you are accelerating. The down side of having such a filter in the exhaust system is very restrictive to gas flow and this limits the car in terms of power. This restriction on the exhaust system will also mean that the engine and particularly the turbo have to work harder which means a reduction in fuel efficiency compared to the same vehicle without a DPF. The reduced fuel efficiency becomes more apparent as the filter gets filled up and therefore more restrictive.

In order to efficiently burn off the particle matter inside of the DPF, the engine needs to be hot. Some car owners are unaware of this and it is because of this that some owners are having problems earlier than they might expect (as some drivers aren’t aware they have a DPF on the car in the first place). Obviously, to get a car to a high temperature, it needs to be driven. For the first 10 minutes of any journey from a standing start and this is when the car emits the most emissions and so, if your car is only being driven for short journeys, to the market and back, to drop the children off at school or even on just some slow-paced city driving, the engine will never get hot enough to burn off the particles in the filter. It is this kind of driving that spells more problems with DPFs than anything else.