A guide to buying turbo diesel cars

Gone are the days when a diesel truck was the only vehicle on the road which burned oil. Even prestige manufacturers have jumped on the bandwagon and diesel sales are increasing. Indeed, Jaguar's diesel cars are among the best selling in their range. So, what do those of us considering ditching petrol engines for diesel need to be aware of?

How do petrol and diesel engines differ?

How does a diesel engine work? Petrol engines rely on ignition of the fuel/air mixture using a spark plug in the cylinder. In this case, the fuel is injected into the air flow outside the combustion chamber. Diesels differ in that they rely on engine compression to supply the heat and diesel injectors fire the fuel directly into the cylinder. The rest of the diesel cycle is similar to its petrol counterpart. In a turbo diesel car, a turbo is used to speed up the intake airflow by utilising the exhaust gases to turn a turbine screw. The ability to take in more air means that turbo diesel torque and power are greater than non-turbo versions.

What to look out for

When buying a turbo diesel car, you need to perform all the checks you would when buying any vehicle. In addition to these, there are some specific areas that will need to be assessed. Diesel compression is so high (up to 25:1 as opposed to 11:1 for petrol) that components have to be more durable. This means that diesel motors tend to last longer between rebuilds. However, they cost far more when this is required. As a result, any abnormal signs of wear will indicate big bills on the way. So, these should be avoided. Diesels are also much heavier than petrol cars and wear to suspension and steering can be more rapid. Watch for the condition of tyres as accelerated wear rates mean frequent replacement. Turbo seal wear is an issue with both petrol and diesel and can be detected by the appearance of excessive smoke in the exhaust gases.

Diesel tuning

The diesel industry has quickly awoken to the possibilities for extracting more power from these tractable engines. Standard models are supplied with car ecu chips which offer a balance between power, economy and engine life. Diesel remap chips are replacements which can give more miles per gallon and greater power. The popularity of turbo chips is such that you are bound to come across one when searching for a car. However, beware of the effect these may have on your factory warranty or insurance premium. Final word It looks like diesel is the way forward with even racing cars using the technology. Just exercise care when dipping your toe in this growing pool.