Diesel sales are booming all over Europe, with good reason. Though these engines are almost always more expensive to buy than petrol engines, because they are more expensive to produce, fuel economy is between 20 and 30 per cent better than equivalent petrol units.
This used to mean suffering a lot of extra noise and sluggish performance but that is no longer the case and the latest generation diesels give little clue to the fact that there is anything different under the bonnet – if anything, it will usually only be that they have a deeper sound.
Many dealers will sit you down and do calculations based on your mileage to point out that you will never get the difference in cost back on fuel savings. However you will get a substantial lump of it back, good diesels currently hold their value well and the best of them are so much nicer to drive than petrol engines of similar, or even inferior, economy that these facts alone can make them worth more.
This is particularly true of smaller cars where the diesels have a much more drivable nature than small petrol engines can manage. Indeed, on car press launches it is increasingly common for the after drive talk among journalists to be how the diesel is the best of the bunch. There are even hot hatch, convertible and roadster diesels now, offering style and sporty performance with high economy.
If you need or want a 4×4, a diesel is really the only sensible option, bringing fuel consumption into affordable realms and significantly improving its resale values (if a buyer can afford petrol off-roader consumption, they can afford to buy a new one). Diesels also have the ideal power delivery for the towing and off-road work these vehicles do in rural areas.
Despite the view of diesel cars above, if you do very low mileage in an ordinary car it can be difficult to justify the extra cost of a diesel and most car models come with a much wider range of petrol engines.
Increasingly, the larger petrol engines are designed for flexibility rather than power while modem fuel systems, like direct petrol injection, drastically improve fuel efficiency.
A few cars are powered by petrol electric hybrid systems, with the first diesel electric hybrid not far off. Here the conventional engine is supplemented by an electric motor with a battery pack. The petrol engine charges the batteries and cuts in when the power demanded is more than the electric motor can deliver. They are popular in America and Japan (where diesels are unpopular for historical reasons) and with Westminster politicians because they can look green while avoiding London congestion charging, but it is debatable whether their exemption from the charge is justifiable.
The theory is that at low speeds they run on non-polluting electric power but in practice they can only do this at very low speeds and when fully charged, so much of the time they run on petrol or a combination of petrol and electric. True, the petrol engine cuts out when the car halts in traffic jams and restarts automatically, but there are conventional engined cars that do that too, and there is nothing to stop you turning the key.
However, their biggest drawback is cost. The difference between petrol and petrol electric can be more than five times the difference between petrol and diesel, yet fuel economy is not as high as a good diesel so emissions, except in electric only moments, are no better. There are also concerns about the high-energy use during manufacture and recycling batteries.
Read more about Top 10 Most Fuel Efficient Cars.