True Or False: Common Perceptions Of Diesel Engines

A decrepit truck belching black smoke struggling to pull its load; that’s the prevalent image many of us conjure in our minds when we talk about diesel vehicles. However, powertrain technologies in the past two decades have made diesel engines sufficiently smooth and refined that they can be used in private passenger vehicles, even luxury ones.

Diesel vehicles have been making some inroads into Malaysia in recent years, but the mass market continues to view them with scepticism and pre-conceptions. In this article, we examine some common perception of diesel engines and see what’s true versus what’s not:

1.Diesel Engines are Dirty: True in the old days, but not anymore. Introductions of turbocharging and direct injection technology have revolutionized what’s possible with a diesel engine. Further refinement of the computer-controlled injectors has meant more complete and efficient combustion of fuel, resulting in better and cleaner performance in modern diesel engines.

2.Diesel Emissions – NOx, Diesel Particulates: Diesel engines do emit high levels of nitrogen oxides. Sophisticated emission systems and filters, however, trap these dangerous particulates and prevent them from being released into the atmosphere. Mazda’s SkyActiv-D diesel engines take things further by being able to meet the latest Euro 6 emission regulations even without needing expensive NOx after-treatment. This is because the low 14.0 compression ratio of the Mazda engines allows more uniform combustion that significantly reduces the creation of NOx particles.

3.Better Fuel Consumption: Manufacturers usually publish 25% better fuel economy for diesel engines than a petrol motor of equivalent performance. This is largely true in the real world, but with the caveat that you are hardly likely to ever match the claimed lab-tested figures. Of course, driving style plays a part too; the more aggressive you are with the throttle, the more fuel you burn - but you do burn less driving a diesel.

4.Diesel Engines are Noisy: It can’t be helped. The moment you fire up a diesel engine, you are greeted by that familiar clattering sound. It is an inherent characteristic of a diesel engine that you simply have to live with. That being said, car makers have been working very hard to refine the behaviour of diesel engines on the move. So, whilst your diesel car does sound a little like a lorry on idling, rest assured that most of them are as quiet and as refined as you can wish for when you get going.

5.Poor Overall Performance: We all know about the superior torque of diesel engines, but many enthusiasts continue to dismiss diesel engines because they don’t rev as freely nor respond as quickly as a petrol engine. Not that these concerns have no basis, but they are increasingly less valid. Innovations such as two-stage turbochargers allow diesel engines to generate all its peak torque from increasingly lower rpms and speed up response at the same time. In our recent experience driving the Mazda 6 Diesel, the 2.2 SkyActiv-D engine responded with a linearity that is almost reminiscent of a petrol engine.

6.Maintenance Cost: You win some, you lose some. Maintenance cost of diesel engines are traditionally higher than petrol vehicles, but the gap has shrunken considerably over the years. Oil changes cost more in diesel vehicles, and there is also inevitable servicing cost of the turbocharger and diesel particulate filter which you don’t worry about in a petrol engine. That being said, you don’t have to bother yourself with having to change spark plugs in a diesel.

7.Diesel Engines are Heavy: Because of their naturally high compression, diesel engines need to be made much tougher than their petrol counterparts, and are thus naturally heavier. Remember that this added weight sits up front, which in turn inadvertently blunts handling and responsiveness. Mazda’s SkyActiv-D diesel engines are not affected by this concern, however. Because its compression ratio is lower than regular diesel engines, a Mazda SkyActiv-D powerplant does not need to be as heavy.

Premium marques such as Mercedes-Benz, BMW, and Porsche boast strong portfolios of diesel-powered passenger cars in Malaysia. Mazda, however, is looking to become the next big thing in the diesel market with a complete range of diesel vehicles that starts with the Mazda 6 and CX-5 launched recently and set to be followed by the Mazda 2 and CX-3 in due course.