Fuelling The Debate: Petrol v Diesel

Diesel or Fuel?

There are almost 10,000 different types of car currently toddling around Britain’s roads. That’s a lot of choice.

Very often, however, the choice of which used car to buy often comes down to one simple decision: petrol or diesel. A decade ago the decision was relatively straightforward: short journeys = petrol, long journeys = diesel. However, changes in technology, travel patterns and fuel costs have muddied the water no end. In this feature, VCARS take a new look at the pros and cons of the old quandary… and find there’s less and less to choose between the duelling fuels.

Price to buy

Used and new diesel cars often carry with them a £1-£2,000 premium. The premium is due to diesel’s ability to retain value and the traditional cheaper running costs. The additional outlay is usually recouped by those cheaper running costs. This only kicks in, however, for drivers covering over 11,000 miles every year and, on average, can take six or seven years.

Winner? On balance, Diesel


Running Costs

In 2003, the average price of petrol was 77.5p per litre and the average price of diesel 75.7p per litre. In 2013, the price of petrol is 137.9p per litre and diesel 144.9p.

Diesel drivers used to walk away from pumps feeling quite smug: not only had they saved money while buying fuel, their diesel cars would go further per gallon. You’ll still get greater mpg on most diesel models but the growing fuel price means it take a lot longer to make up the difference – and, in general terms, only if you’re doing the distances mentioned earlier. Think about it, do you really do 900 miles a month, 225 miles a week, 45 miles a day – that’s a decent distance for anyone who doesn’t hit the motorway quite regularly.

Did You Know? In May 2012 51% of new cars were diesel, 47.5% were petrol. 1.5% alternative fuel sources.



Taxing & Re-sale

Diesels are often more efficient than petrol and CO2 levels lower (after they’ve been filtered). As a result, the car tax liability is also often less. Similarly, diesels retain their value better than petrol.

Did You Know? Diesel was the family name of German inventor Rudolf Diesel who invented the diesel engine in 1892.



Servicing and Repairs

Ask most mechanics and they’ll tell you that diesels are more complicated than their petrol counterparts. Diesel engines are also slightly less reliable than their petrol siblings and particularly expensive when something serious happens.

Consider that, in 2009, a European directive said Diesel Particle Filters had to be fitted to all diesel exhausts. DPFs trap bits of soot. They have to be emptied regularly and this is done by burning at high temperatures. Your exhaust will only reach those temperatures during journeys of around ten miles or more. If you’re not doing those distances, diesel drivers might encounter problems – the AA get around 700 call-outs for problems related to DPFs every month. The year after next, Euro emissions are demanding a Nitrogen Oxide traps – these will remove the nitrogen compounds from exhaust fumes… diesel engines are getting more and more complicated. And with complications come problems.

Winner? Petrol




Diesel engines offer more pull from lower revs which make them a favourite when towing, or overtaking at lower speeds. In the main, they offer better mpg and better eco credentials. It used to be that diesel made an ungodly racket, not any more. Modern diesels are smooth and silent. However, if you want thrills, it’s got to explosive petrol.

Winner? Still Petrol



Received wisdom is that diesels make sense in the medium to long-term. Last year Which? compared the payback credentials of petrol v diesel  across six models. Their findings were common-sense-bustingly  curious. They calculated the fuel bill on just over 10,000 miles and discovered that in four of the six cars, petrol worked out cheaper! Which? found it would take a BMW 530d SE diesel auto 14 years to be as cost-effective as a 528i SE Step petrol auto. The 308 SW 1.6 3-HDi diesel would take three years to match the petrol 1.6Vti. The 1.6l Ford Fiesta TDCi took almost 8 years to be more cost effective than the 1.25l.

Winner? More recently, Petrol.



The short-journey petrol v long-journey diesel edict still applies but the gap continues to close. Petrol engines like Toyota’s Aygo has diesel-busting mpg (and that’s before 2014 introduces cars like VW’s XL1 100mpg hybrid) and pose a real option for the frugal driver. Diesel is no longer simply the first choice for cost-conscious drivers. However, those looking for smooth driving performance, particular at lower revs, can increasingly consider diesel.

Now, what about electric cars…


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