I recently bought a Mercedes C320 CDI to last throughout my retirement. I obviously wanted a car that will last a long time but since then I’ve seen a TV programme where the subject of petrol vs diesel was discussed.
The general opinion was that a dieselpowered car was not the solution if one wanted to keep a car for a long time. Since then I’ve kept my eyes open for old turbodiesel cars on the road and found that they are very scarce indeed.
Did I, therefore, buy the wrong car? Should I rather have bought a petrol-engined car? Is the turbo the problem, and are these items also unreliable on petrol-engined cars?
CHRIS ALBERTYN – By e-mail
Modern automotive diesels often run at boost levels of over one bar and this means they are more highly stressed than some of the high-output sportscar engines in terms of average pressure on the pistons (see next letter for more on this subject).
It also means they are more easily damaged by indifferent or ignorant servicing methods. For example, a blocked air filter that will cause a petrol engine to run rich, and therefore use more fuel but run cooler, will cause overheating on a diesel engine, and the first component to suffer will be the turbocharger.
Unfortunately, to judge by some of the complaints we get, some dealers employ service personnel that have had the absolute minimum amount of training.
Petrol engine turbos are also highly stressed, but everybody realises that they’re high-performance engines, so that they’re usually serviced by specialist workshops.
If you stick to the recommended service intervals and are in the care of a good dealer you may end up with a reliable diesel.
