Weigh up the costs when choosing a new car

When it comes to buying a new set of wheels, most of us will spend hours deliberating over the make and model before signing on the dotted line.

As a motorist, there are all sorts of factors to take into consideration, such as price, reliability, fuel efficiency, the insurance premium, and how much it costs to tax.

Here we take a closer look at some of these factors, to see which cars deliver the best value-for-money, and which motors you might be better off steering clear of - because they'll leave you out of pocket.

All the findings in this article are based on 12 models (*) - Ford Fiesta, Ford Focus, Ford Ka, Ford Mondeo, Mini, Peugeot 206, Renault Clio, Renault Megane, Vauxhall Astra, Vauxhall Corsa, Vauxhall Zafira and Volkswagen Golf.

MOT failure rates

MOT failure rates have long been a well-kept secret, but figures showing the vehicles that most frequently pass - and fail - the test were recently made public (**).

The MOT is the annual test of road-worthiness that all cars must pass once they are three years old and is an indicator of a cars' reliability.

According to the findings, some of the country's best-selling cars are failing their very first MOT, despite being just a few years old, and for popular cars first used in 2004 and tested in 2007, the worst performer is the Renault Megane which had the highest failure rate at 28.1 per cent.

This was followed by the Vauxhall Corsa in second position with a failure rate of 24.7 per cent and the Ford Mondeo at 21.8 per cent.

At the other end of the scale, best performer is the Ford Fiesta which had the lowest failure rate of just 15.6 per cent, putting it just ahead of the Ford Focus at 18 per cent and the Vauxhall Astra at 18.4 per cent. (See: How the car you drive affects the insurance premium you pay.)

Motor insurance premiums

Car insurance premiums have been climbing for months, and new research shows motorists renewing policies now face the largest annual hikes ever recorded, with the average insurance premium now standing at £564.69 - a 19.6 per cent increase from January 2009 (***); the main factors fuelling these increases are the rising cost of personal injury claims and fraud.

While premiums may well be rising, the make and model of the car being insured also plays a significant role in determining the price of your policy.

If you compare the average premiums for "all customers" over the whole of 2009, the most expensive model to insure is the Vauxhall Corsa with a policy costing £818.22, followed by the Renault Clio at £766.45 and then the Volkswagen Golf at £753.99. (****)

If you don't fancy forking out quite so much on your car cover, the cheaper options include the Vauxhall Zafira at £379.29, the Ford Mondeo at £431.64 and the Renault Megane at £459.81. (****).

Road tax rates

Road tax - or Vehicle Excise Duty - has to be paid to acquire a licence for most types of vehicles if they are to be legally used on public roads, and, since 2001, rates have been determined by CO2 emissions and type of fuel used.

Based on the rates effective from April 2010, the most expensive cars to tax are those which fall into "band I" - including the Ford Mondeo and the Vauxhall Zafira - where the cost is £110 for six months or £200 for 12 months.

The cheapest cars to tax are those that fall into "band F," and these include the Vauxhall Corsa, the Ford Ka, the Peugeot 206 and the Ford Fiesta, where the cost is £68.75 for six months and £125 for 12 months.

Winners and losers

With so many factors to take into consideration, buying a new car is certainly not a decision to take lightly.

The Renault Megane, for example, is the most likely to fail its first MOT, and while it's among the cheaper models to insure, it is middle of the table for road tax.

The Vauxhall Corsa and Renault Clio also fare badly overall, with high rates of MOT failure and high car insurance premiums.

At the other end of the scale, the Ford Focus is a good performer in the MOT test, and appears at the cheaper end of the insurance tables for both insurance and road tax.

The Ford Fiesta also has one of the lowest MOT failure rates and is one of the cheapest models to tax, while the Vauxhall Astra is a top performer in the MOT test, and while it's middle of the table to insure, it's cheap to tax.

At the end of the day, you need to ask yourself whether any one of these factors alone are enough to sway your decision, as the MOT figures, for example, give no allowance for mileage or usage, while the price of an insurance policy depends not only on the make and model, but also on other risk factors, such as your age.

The key is to shop around when purchasing a new car so you can be sure of making an informed decision.

(*) The 12 most popular models are based on the 12 most-tested cars - those with more than 20,0000 MOTs in 2007 - source: BBC.

(**) The Vehicle and Operator Services Agency (www.vosa.gov.uk) had resisted publishing the league tables saying the figures might be misleading and could breach commercial confidentiality, but the statistics were eventually released following a Freedom of Information (FoI) request by the BBC.

(***) Independent market research firm, Consumer Intelligence; this research is used by the the Office of National Statistics for its Retail Price Index.

(****) Confused.com data