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525d VS E250 CDI

Slick Battle

BMW's best 5-series now comes in the guise of six-pot diesel. Can it convincingly outwit the Thai market's pioneering diesel luxury saloon?

When Mercedes-Benz opened the diesel fray in the Thai luxury car market with the previous-generation E-class, it took a rather cautious approach with the E220 CDI back then.

Instead of promoting it outright, Mercedes positioned the oil-burning E-class as a sensible option to the petrol variations, which were given more prominence due to the large following of premium car buyers yearning for the three-pointed star marque.

Today, the E-class still receives the same treatment. Despite being the version that offers the most performance of all mainstream E-classes, the E250 CDI is not the range-topper. The honour remains with the petrol E250 CGI in Avant Garde trim (aside the six-cylinder E300).

Archrival BMW has taken a different approach, since it knows that it was second to Mercedes in offering diesel choices to Thai customers. That's why BMW is putting a crown on the 525d, and not the 523i (the numbers on the badges could have also dictated the reason).

Simply put, BMW wants to make its diesel-powered cars look good in the showroom, while Mercedes somehow feels content to leave its oil-burners the way they are and let the buyers do the talking.

Because of that, you may already sensing a win here for the 525d due to its more sophisticated level of features like 18-inch wheels, DVD/GPS audio, four-wheel-steering, three-mode driving style setup, multi-way adjustable front seats and energy regeneration system.

As the Elegance name suggests, the E250 CDI is modestly equipped in comparison. It doesn't get those aforementioned equipment of the 525d but intends to boast safety novelties like driver drowsiness detection system and the so-called Pre-Safe anticipatory kit.

Naturally, there's a price difference of B400,000 between the two - not just because of the standard equipment but also for tax reason. The B3.999m E250 CDI comes with a 2.1-litre engine attracting 35% tax rate; the B4.399m 525d has a bigger 3.0-litre variation, thus 40%.

Despite the different numbers of cylinders and engine capacity, their outputs are nearly the same, and while power is rated at an identical 204hp, the E250 CDI has 50Nm more of torque at a heady 500Nm.

In spite of that, the 525d and E250 CDI feel equally powerful on the move. There's never a shortage of pulling power, even on testing roads such as when driving your family to your favourite mountain resort.

The way the cars accelerate beyond the legal limit is also impressive. They build up speed without effort, although it must be noted that the 525d seems to reach the limit faster even though its figures on paper suggest otherwise.

But the biggest difference between the two in performance is the way the power is deployed to the tarmac. The Bee-em uses a modern eight-speed auto, while the Merc persists with a classic five-speeder.

Never during the 800km test ride up the mountains in Kamphaeng Phet did the BMW's automatic fail to impress. Transmission responsiveness was immediate and shifting quick.

The Benz's unit feels far lazier and slower in comparison. In fact, its gearbox, still in application across the C, E, E-class Coupe' and SLK model ranges, seems dated, and really is starting to haunt Motoring.

Fortunately, the prodigious amount of torque in the E250 CDI slightly helps compensate for this shortcoming. You would only forgive the five-speed slushier if you happen to be one of those very patient and restrained drivers.

Like how we found during a 523i/E250 CGI comparison earlier this year, the cars' roles in terms of driving characteristics seem to have switched, that is, the Merc being the slightly more engaging car to drive with a livelier steering and chassis.

But it's really hard to ignore the BMW's polished driving dynamics which seem to work more effectively for most buyers in the luxury car segment. Grip is aplenty at all times, handling is neat and brakes are progressive.

Although the 525d and E250 CDI don't really absorb road imperfections that brilliantly, the former stands out with a more composed body on demanding roads and long distance driving over the country's infamous patchy network of highways.

For those concerned about gas bills, both Teutons will suffice with their ability to achieve over 15kpl when cruising at high speeds.

While the petrol showdown between the 5-series and E-class saw the former achieving a slim victory (due to its lack of performance), this diesel shootout now sees the BMW scoring a more convincing win over the Merc.

Now, that's only if you're not bothered by the B400,000 price difference.

There’s a greater sense of occasion and higher kit level in the 525d’s cabin. The BMW’s got six cylinders and 3.0-litre displacement producing an identical 204hp.

The E250 CDI isn’t intended to be an E-class range-topper, hence the Elegance trim. Power is derived from just 1.8 litres but twin turbos help yield that impressive 500Nm of torque.