Size matters
Traditionally, cars are split into classes. Using the Ford European range as examples, because everyone knows what they are, the Ka is class A, Fiesta is B, Focus is C and Mondeo is D, and so on. However, many cars now bridge these classes: compact MPVs often sit between classes B and C while some cars, like Ford Focus C-Max, Volkswagen Golf Plus have the space of a D-class or better. Car classes vary in other markets, as do perceptions. The American and Australian idea of a ’small’ car is not the same as the European one. Indeed, the smallest car Ford sells in the USA is the Focus and in Australia it is the Fiesta. But wherever you live, the bigger the car you have, the more money you will spend on fuel, and the more you will be contributing to your world being damaged by people burning more fuel than they need to.
Bigger isn’t better
Generally, the bigger the car the more expensive it is to buy and run, though there are exceptions especially among the latest turbodiesels which often give large cars the fuel consumption more usually associated with much smaller ones: you can now get luxury diesel sports saloons which reach 60mph in less than eight seconds but still do 40mpg.
These days you do not have to buy a bigger car than you need to get a high level of equipment, safety or refinement. Upmarket versions of even the smallest hatches are now very well equipped and, while bigger and more luxurious cars have extremely high levels of safety and refinement, the gap between them and more mundane cars, in this respect, is shrinking. There are plenty of small hatchbacks in which you cannot hear the engine at motorway speeds, while wind and road noise are also subdued. Manufacturers these days often compete with each other to be able to boast ‘best safety in class’.
Bigger inside
So, your first consideration is to work out how big a car you need. Even if you have a family and need space in the back, don’t discount B-class hatches – some have a lot of passenger room for their size. Indeed, many of the latest have more room in the back for long legged people behind a tall driver than some much larger executive saloons. A good indicator of interior space is wheelbase, the measurement between the front and rear wheels. The further the wheels are apart, the more room there is to put things between them, so if you have two cars that are the same overall length, the one with the longer wheel base is likely to have more space. But also consider how this space is used. If you are very tall and have no children, maximum room in the front may be more important to you.

A small, economical engine might haul your chosen car happily through town traffic but if you do a lot of motorway driving it could prove frustrating and a false economy.
Balance of power
Do not assume that the smallest engine is always the most economical. There is an optimum engine size for the car and the work you intend to do. For example, there is a 1.5 turbodiesel engine used by Nissan and Renault that is available in two power outputs, and the fuel consumption figures show only slightly better fuel consumption for the more powerful one. But on the road, while both do around 60mpg in town, taking them onto a motorway sees the lower powered engine’s fuel consumption drop more markedly than the more powerful version’s.
In general, a more powerful engine is working less hard when maintaining cruising speeds and accelerating up to speed on faster roads. Similarly, if you want to tow or carry heavy loads, a more powerful engine is likely to manage it better. If you only want to potter around town, however, you’d probably be best opting for the smaller engine, which should still prove more economical.
Understanding figures
So how can you tell what engine will suit you best? It helps to understand the engine performance figures quoted in brochures and road test articles. Most people understand ‘power’, usually expressed as brake horsepower (bhp) or kilowatts (Kw), though you may also see it as PS which is the abbreviation for the German word for horsepower. A kilowatt is 1.341 bhp while 1 PS is 0.986 bhp. This is power like a racehorse going flat out, carrying the car on to its maximum speed.
Car specifications show these figures as ‘X bhp or lb ft at Y,000 rpm’. This means that the engine develops its maximum power, or torque (represented by ‘lb ft’ – see below), at that many engine revolutions (revs) per minute (rpm). This can give you important clues as to how that engine feels. Generally, if the engine revs shown are high, it needs to be worked hard to get the best from it.