The pros and cons of choosing diesel.

October 14, 2008 -- Filed under Clean Diesel by Louis-Alain Richard

When the time comes to justify choosing a diesel engine, which is generally more expensive, the classic argument uses clever calculations about annual distance travelled and the cost price of the said machine. None of that here, mainly because there is no magic formula to determine the exact tipping point where one of the two machines gets the upper hand.

A Question of Economics
If it were only a question of economics, we would all drive micro-cars with tiny gasoline engines, of which there are now a few on the Canadian market that cost barely half the price of a mid-size car. Also, the additional cost of the diesel engine at purchase is usually mostly recuperated at resale, which still complicates the deal even more regarding the calculation of the higher-quoted tipping point. And of course, we worldly people do not like to discuss lowly material considerations, do we?

A Question of Maintenance
So if we put aside the notions of money, what are the other advantages and disadvantages of going diesel? There are of course the traditional arguments of reliability and simplified maintenance, but this no longer really holds true. The best gasoline engines have maintenance schedules similar to those of diesels, and I know of some gasoline cars that can reach the half-million kilometre mark on the same engine. So the score’s even.

Pros
In my opinion, the arguments for choosing a diesel engine revolve around two themes: driving pleasure and environmental footprint. In the first, since diesel engines are well adapted to city driving due to their considerable torque at very low speeds, their quietness and “relaxed” driving are often mentioned. Still, when the time comes to drive a well loaded down diesel or to climb a steep slope, they tend to come through thanks again to their considerable torque.

As far as the environmental footprint is concerned, diesels have some interesting advantages. One can choose a larger car for the same fuel consumption. During short trips, diesels are closer to their official rate of fuel consumption than gasoline engines, mainly because the latter operate in an enhanced mode for the better part of these brief excursions. There is also the “good conscience” factor: if you choose to drive a huge luxury car, you can still be responsible by choosing the engine with the lowest greenhouse gas emissions, and usually this is a diesel. At least this is the argument that I was given in France to explain why the great majority of sedans and luxury SUVs are powered by diesels.

Cons
Now for some of the disadvantages to this type of vehicle. First of all, modern diesels are allergic to poor quality fuel: using heating oil or restaurant waste is out of the question, as serious damage could be done to intake and anti-pollution systems. There’s also the fact that their reaching optimal temperature is longer than for gasoline engines. This doesn’t impact on consumption or durability, but it makes the heated seat all the more appreciated. And the traditional automatic gearbox must be abandoned, as this type of transmission cancels out part of the fuel efficiency and the “turbo” effect. But this applies to all transmissions, for gas or diesel engines, with the exception of direct-shift gearbox (DSG) and continuously variable (CVT) transmissions, which are almost as efficient as manual transmissions.

Sports Talk
Finally, on a lighter note, the racing world has been debating the diesel question for several years. Not Formula 1, of course, but rather endurance racing, a type of competition in which distances travelled exceed 5,000 kilometres in just one day, like the 24 Hours of Le Mans. The pro-diesels (Audi and Peugeot) invoke commercial reasons and the connection between racing and marketing, the famous principle of “Win on Sunday, sell on Monday.” Those against diesel say that these cars don’t have a sporty sound (even though they have 12-cylinder engines equipped with turbos), that their greater autonomy on the track and their phenomenal torque increase the risk of flats as their tires are so intensely used for such a long time, that “oil burners” aren’t very sporty, and so on. Nevertheless, since 2006, it’s the diesel that’s had the upper hand. Which just goes to show that you need more than just luck to win. You need diesel

And you, are you for or against the introduction of these new diesels?

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