Which is better?

If you're in the process of buying a new set of wheels you may be faced with the dilemma over whether to opt for a car that runs on petrol or diesel.

Diesel cars are currently in high demand as more and more people look for better fuel economy - viewing diesel cars as a more cost-effective way to drive than their petrol counterparts.

However, the argument is not clear-cut.

When selecting a new car from the thousands of models out there, one of the major factors will be the initial outlay, and then day-to-day running costs.

Here we take a look at the buying and running cost differences between petrol and diesel vehicles to help you decide which option is the right for you.

Initial purchase costs

At the outset, diesel vehicles tend to be pricier to purchase. However, these vehicles usually have a longer life-span and also depreciate in value more slowly than their petrol counterparts.

This is an important factor to bear in mind, as depreciation can be one of the biggest costs of buying a new car. Further, it's worth noting that diesel cars can also be more expensive than petrol cars even if you're buying a used model.

Fuel economy

When it comes to putting diesel into the tank, this can cost more than petrol.
That said, diesel vehicles tend to be more economical with their fuel - meaning petrol cars often work out more expensive in the long run.

However, as a driver you need to be aware that it could take several years of fuel-efficient motoring to make buying a diesel vehicle worthwhile.

In fact, according to experts, unless drivers do 10,000 miles for a used diesel car or 6,000 for a new diesel car, they will not recoup the cost.

By contrast, if you're only planning to keep your car for a few years, or if you're a low-mileage motorist, you may be able to make savings by opting for a petrol model.

In the wake of soaring petrol prices, if you're looking to save money on fuel bills, you need to work through these scenarios carefully.

Car insurance

When choosing between a petrol and diesel car, you not only need to take into consideration the mileage and fuel costs, but also the cost of cover.
Insurance can be more expensive for diesel cars, costing around 10-15% more than it would to insure an equivalent petrol car, according to experts.

This is because diesel cars have higher average accident repair costs, and because insurers must factor in the higher overall replacement cost if a diesel is stolen.

Further, as diesel models have become smoother and more powerful, underwriters no longer view these vehicles as a less sporty alternative to petrol models.

Crucially, when buying car insurance for any type of vehicle, you need to shop around, comparing the cost and levels of cover from a range of providers; a price comparison service such as MoneySupermarket.com could help you to find the best-value policy for your needs.

Road tax pricing

When it comes to road tax, prices are calculated based on C02 emissions, with cars that produce less C02 invariably attracting cheaper road tax prices.

In the petrol vs. diesel debate, diesel vehicles win over petrol cars. This is because diesel vehicles are more efficient than their petrol opposite, and emit less C02, so often attract cheaper road tax.

When choosing a new vehicle, it's worth finding out the road tax band your car of choice is assigned to; you can do this at Direct.gov.uk.

Armed with this knowledge, you can then see how much it will cost annually for road tax.

Servicing costs

Generally speaking, diesel cars don't need to be serviced as frequently as petrol cars which can mean diesel vehicles cost their owners less. However, you need to bear in mind that diesel servicing costs, when required, may be more expensive.

As a result, over a three or four-year term, you're unlikely to see a significant difference between servicing costs for equivalent petrol and diesel cars.

Further, while many motorists believe that diesel engines stay reliable for longer, in reality, modern petrol engines are likely to be equally reliable; petrol engines are also likely to be cheaper to repair if anything major goes wrong.

Petrol vs. diesel - which is cheaper?

When it comes to choosing between a petrol vehicle and a diesel vehicle, there is no right answer.

The majority of us still drive petrol cars - and for low-mileage motorists, this still makes sense.
And even though diesel cars are less damaging to the environment and now run as quietly and smoothly as their petrol equivalents thanks to the advancement technology they are unlikely to work out cheaper in the short run.

However, over the medium to longer term, and particularly for those who have a high annual mileage, a diesel car could prove better value.

Crucially, the choice will depend on the vehicle and you, the motorist.

†82% of shoppers obtained a quote in 5 minutes or less. Source eDigitalResearch December 2012.