2009 BMW 335d and X5 35d: Is diesel the logical choice?
The next time you find yourself in a BMW showroom, it is a safe bet that the representative will talk to you about its two new diesel models. So you will be tempted to jump toward this engine type that is so popular in Europe, where 70% of the vehicles sold are equipped with diesel engines. That is how North America, where this type of engine represents barely 15% of sales, differs radically.
Since Volkswagen always relies on this technology and Mercedes-Benz has been offering more and more diesel models for some time now, it isn’t surprising to see BMW respond in an attempt to profit on the increasingly keen interest in this engine type.
Why not?
When looking at the 335d sedan or the X5 35d SUV, two new BMW models equipped with six-cylinder diesel engines, you are surely going to ask the representative why you should opt for this type of engine. He'll undoubtedly tell you that you’ll get better fuel economy, since a diesel engine consumes less per litre over 100 km. You will bring to his attention that, for a little while now, the price of diesel fuel is higher than that of regular gas, about 10 cents per litre with things as they are. And you are right.
The main reason for this difference is that in North America, contrary to the situation in Europe, more petrol is refined to make gasoline than diesel. Moreover, a large amount of the diesel that is produced is exported while gasoline is imported in return, which contributes to the continued high price. Experts predict that prices will soon be practically equal, but for now, this is not so.
The higher price notwithstanding, when certain conditions are met, you will indeed get better output from a diesel engine. First of all, you have to plan to keep the vehicle longer, which will make leasing it less attractive. What's more, if you only drive it a few thousand kilometres per year or you only drive between the suburbs and downtown, the diesel engine will not be the best fit either. Using the diesel becomes more economical the more you drive, especially considering the fact that the price of the two models is higher than that of equivalent models equipped with traditional gas engines. In the case of the 335d sedan, the price tag is about $800 higher compared to the 335i and $4,000 higher in the case of the X5.
Performance advantages?
So, if there are no real dollar savings on the bottom line, what is the point of opting for this type of vehicle? What is appealing is the phenomenal torque produced by diesel engines compared to gas engines. In the case of the BMW 335d and the X5 35d, both come with a 3.0-litre inline 6 and two-stage turbocharger featuring 265 horsepower for a torque of 425 lbs-ft. The horsepower is hardly impressive, but the torque is outstanding, giving the vehicle more honest accelerations at lower revs. With the exception of enthusiasts, it is rare that people use their engines at higher revs, where all the power is available. In the case of the diesel, a simple acceleration even at low revs will be enough to pin you to your seat. Basically, at BMW performance is everything, so this is where its diesel engines excel.
We had the chance to test drive the BMW 335d and the X5 xDrive35d for a few hundred kilometres. First of all, I must admit that the ride of these two models is very straightforward compared to the gas model. It starts instantly, even when cold. In the past, their sound made diesel engines easily recognizable, you know doubt recall the knocking sound caused by the pistons bumping against the cylinder walls. BMW succeeded in minimizing the knocking sound by offsetting the piston attachment slightly, and with the help of other features the diesel engine is practically as quiet as a gas engine.
On the road, we like the engine's generous torque, which transmits power quickly and without hesitation. One of the key features is undoubtedly the use of two turbochargers. This is also the case with the 3.5-litre, six-cylinder gas engine, but unlike the gas model, which uses two identical turbochargers (one per row of three cylinders), the six-cylinder diesel includes two in series. Since a diesel engine produces less heat, thus less pressure for the turbo, the engineers decided to use a small turbo that initially requires less pressure to activate it, and a bigger one that becomes more efficient at higher speeds. This combination helps reduce the lag time from when the accelerator is pressed and when the power arrives, ensuring a superior output at high speed.
All of which helps propel the sedan 335d from 0-100 km/h in 6.2 seconds, which is a mere half- second slower than the regular 335 while the X5 covers the same distance a second faster than its gas counterpart. Who says that diesel and performance are incompatible? Try telling that to Audi, which is taking home all of the honours in Le Mans Series with its R10 TDI.
What about both vehicles?
In my opinion, the X5 35d SUV in particular should attract the most attention from buyers. As is the case at Mercedes-Benz, SUVs seem to be better accepted with a diesel engine under the hood. The 335d sedan is nice too, but only the front-wheel drive version is offered with a diesel engine, while the all-wheel drive versions represent practically half of the sales in Canada. This choice is dictated mainly by our neighbours to the south, since the diesel engine's arrival in Canada was influenced in large part by its introduction in the US. What's more, it is only offered with an automatic transmission since no standard could handle this much torque.
As for the X5, the availability of a diesel version gives those who need to tow heavy loads a very interesting choice. While a gas engine's fuel consumption tends to rise quickly with increased load, the diesel engine will have much more reasonable consumption. Regardless of the engine however, the towing capacity is the same.
Need to know
In order to meet new environmental standards, BMW had to incorporate various technologies in its vehicles. While Mercedes-Benz includes all of these features under the term Bluetec, BMW uses the name BluePerformance. Thanks to these systems, modern diesel engines are very clean. One of the key components that help reduce emissions turns out to be a fluid that is injected into the catalytic converter and helps break up carbon monoxide atoms and transform them into nitrogen and water vapour. This “Diesel Exhaust Fluid”, as it has been baptized, is found in two tanks which you will have to fill every 20,000 kilometres or so, since once they are empty, the car will not be able to start. But fear not, you will get several warnings beforehand, and the price of this liquid is not every high, about $20 will fill the tank, but you have to take it into account.
In conclusion, deciding to opt for a diesel engine depends on several factors, most notably the primary use of the vehicle. The manufacturer promises 30% less fuel consumption than a gas engine, but you will have to verify that assertion. The savings that are promised do not always turn out to be accurate, as we were able to prove during a comparison between the gas and diesel versions of the Jeep Grand Cherokee done by my colleague Antoine Joubert and published in the Guide de l'auto 2008.