Buying

If you are thinking about purchasing a new car then even the most basic research will reveal that on average a diesel car can cost around 1,400 more than its petrol equivalent.

The initial cost that choosing diesel over petrol incurs can eventually be recouped due to diesel engine's better fuel efficiency. However, latest figures suggest that it could take driving as many as 45,000 miles before your diesel car would begin saving you money.

In the second-hand market, choosing a diesel engine model over petrol begins to make more sense. There's a couple of reasons for this:

  1. 1.

    Second-hand diesels tend to be more in demand because of their reputation for providing better economy and having lower tax rates thanks to their lower CO2 emissions.

  2. 2.

    The perception that diesel engines are more reliable than petrol ones.

You are also likely to find that your brand new diesel has retained more of its value when you come to sell it on.

Something else to consider if you are buying new is the cost of servicing your vehicle. Although the period between services tends to be longer for diesel engines, the cost of the parts are often higher - whereas petrol engines need to be serviced at shorter intervals, but the parts are cheaper.

Verdict: Score draw.

Driving

The old perception that diesel engines are noisier, slower and dirtier than their petrol equivalents no longer holds quite as true.

A new generation of turbo engines from car manufacturers are proving to be more than a match for their petrol equivalents; matching them in terms of performance, smoothness and noise levels. Diesel engines are also able to produce high torque at low speeds and so are good for overtaking.

Verdict: Draw.

At the pump

Unfortunately, the days of diesel being cheaper at the pumps are long gone. Never ones to miss out, the petroleum companies and government were quick to take advantage to diesels renaissance as a cleaner alternative to petrol.

Currently the difference in price between diesel and petrol stands at about 2 pence per litre. You will also find that diesel tends to be sold through less pumps on forecourt - which, in an era where every petrol station has a shop, means longer times queuing times for diesel owners.

What is interesting to note is that while Britain has only the tenth highest price for unleaded petrol in Europe, it has the second highest diesel price. This is something to bear in mind if your are travelling in Europe.

Verdict: Petrol wins!

Mileage

This one is a no-brainer as Diesel engines generally get you an average of 15 to 20% more miles per gallon than their petrol equivalents (depending on how they are driven).

But be aware that petrol engines are catching up in terms of mileage by using smaller, more efficient, turbo-charged engines. Although they still have some way to go to match the likes of Volkwagen's latest Golf BlueMotion 1.6 TDI which offers an amazing 74.3 mpg and has a theoretical range of 899 miles!

Verdict: Diesel wins!

Environmental impact

Similarly to the issue of mileage, this is also a bit of a no-brainer. Diesel's greater efficiency means that its CO2 emissions are 20% lower than petrol.

However, diesel does produce a harmful by product in the form of tiny particles which have been linked to breathing disorders like asthma. Manufacturers have tried to tackle this issue by fitting vehicles with particle filters and catalytic convertors, but ironically this has caused some reliability issues with certain models.

Petrol vehicles are closing the gap in terms of environmental impact by using hybrid engines. The introduction of sulphur-free petrol in the near future will help further reduce the environmental impact of petrol.

Verdict: Diesel wins!

Tax and duty

With regards to road tax, diesel's lower CO2 emissions means that diesel drivers are rewarded with lower tax bands than petrol owners. Unfortunately, the government's generosity towards diesel does not also extend to fuel duty. Hauliers are currently lobbying parliament for a reduction similar to road tax in fuel duty on diesel to reflect its greener credentials - but don't hold your breath!

Verdict: Diesel wins!

What alternative fuels are there?

There are alternatives out there to petrol and diesel, such as:

  • Liquid Petroleum Gas or LPG: LPG costs half the price of diesel or petrol and has significantly lower CO2 emissions. Most petrol engines can be converted to run on LPG which involves a one-off conversion cost of around 1,600. This means that your engine will be able to run on petrol and LPG which are stored in separate tanks.

    The major drawbacks for LPG are its limited availability (only 1,400 refuelling stations in the UK) and its poor fuel economy which is approx 20% lower than petrol.

  • Biodiesel: Biodiesel can be used with little modification needed to the engine. Biodiesel ranges from 100% pure to a 20% mix with standard diesel. Like LPG the advantages of biodiesel is that it has very low carbon emissions (pure biodiesel is 100% carbon neutral), but also suffers from a lack of availability.

And the winner is?

Both diesel and petrol offer their own unique advantages to the motorist. Diesel's superior fuel consumption is a big selling point, but because of the higher cost of diesel cars it only really makes sense to drivers who are clocking up over 15,000 miles a year. If you are a low-mileage driver then you may find that switching to diesel makes less sense, as you are unlikely to feel any short-term benefits.

However, any gap between diesel and petrol in terms of performance, efficiency and environmental impact is narrowing all the time. Soon your decision could come down to little more than personal choice - say, choosing diesel to reduce your carbon footprint while accepting that you'll be paying more at the pump.

money.co.uk verdict: Fighting draw!