Sunday, April 14, 2013

Fuel consumption: 520d / 525d xDrive Touring

In 2010 BMW introduced its current 5-series, internally designated as the "F10" (sedan) and "F11" (Touring). Guitigefilmpjes has hit the German Autobahn with both the 520d F10 and 525d xDrive Touring F11 in order to see how the fuel economy is when driving at high speeds and if the engines live up to its expectations. Technical details can be found below:

Engine: 4-cylinder diesel engine (1995 cm³
Transmission: 8-speed automatic transmission
Performance: 184hp / 380nm
0 to 100km/h: 8,1sec
Top speed: 227km/h (142mp/h)
Fuel tank (US gallons): 70 liters (18.5 US gallons)

Fuel consumption depends on many different factors, among the tire pressure / size of alloy wheels, the weight of the car (4 people with bagage or travelling alone), the driving profile is the most important determinant of the result. Therefore you can find the driving profile during this trip below:
  • 500 kilometers (310 miles) Autobahn at high speeds, 180km/h and more
  • 200 kilometers (125 miles) Autobahn between 100km/h and 130km/h 
  • 150 kilometer secondary road between 80km/h and 100km/h
  • 45 kilometer city traffic in normal conditions, outside rush hours

The total trip compromised of 895 kilometers (560 miles), and in contrast to previous tests where I tried to achieve the best possible consumption, this time I drove to travel as fast as possible (sticking to speed limits where they apply). 
Driving at high speeds always leads to a higher consumption, but in the 520d the relatively small engine has to work hard to power the heavy 5-series. This has resulted in an average fuel consumption of 8,7l / 100km (27mpg US), which is a far cry from the 5,4l / 100km (43,6mpg US) when trying to drive as economically as possible. 

Engine: 4-cylinder diesel engine (1995 cm³
Transmission: 8-speed automatic transmission
Performance: 218hp / 450nm
0 to 100km/h: 7,2sec
Top speed: 236km/h (148mp/h)
Fuel tank (US gallons): 70 liters (18.5 US gallons)

As new government regulations tax CO2-emissions increasingly heavier, car manufacturers are looking for new ways to cut these. Efficient Dynamics was introduced by BMW several years ago to reduce both fuel consumption and CO2-emissions, so that they would fall into the lower green A- and B-labels that are obligatory in Europe (these labels measure fuel consumption, where the green A-label is the best, and the red G-label the "worst"). By falling in these lower categories, many countries offer tax discounts on these "green" vehicles, making them financially attractive to many customers.

Downsizing is another method used to cut CO2-emissions and fuel consumption. Many car manufacturers, especially in Europe, are replacing engines with smaller engines that use a turbocharger to maintain the same level of performance. BMW has done the same with the 525d, when the 5-series was introduced in 2010 it still features a 6-cylinder 3.0 liter engine. In 2012 it was replaced by a 4-cylinder 3.0 liter engine, the same in the 520d but then with an added TwinPower Turbo (Two-in-one turbocharger).

On paper the figures look good, the engine becomes more efficient while even increasing performance (204hp against 218hp now). However, in reality there are some drawbacks to downsizing. As the 4-cylinder engine is smaller, it has to work harder and shift more often to achieve the same acceleration and speed as a larger 6-cylinder engine. In Germany tests have been comparing the 4-cylinder 525d to the 6-cylinder 530d and found that under the same circumstances, the 530d used 0,5l / 100km less fuel then a 525d.

The exact difference in fuel consumption will depend on the driver, but it is likely that the new 4-cylinder 525d under normal circumstances will not offer a substantial advantage in fuel efficiency. The advantage on paper will result in less fixed costs for the car, but that is it.

When driving a BMW 525d Touring xDrive, I had the following driving profile:

  • 490 kilometers (310 miles) Autobahn at high speeds, 180km/h+
  • 300 kilometers (125 miles) Autobahn between 100km/h and 130km/h 
  • 150 kilometer secondary road between 80km/h and 100km/h
  • 41 kilometer city traffic in normal conditions, outside rush hours

Resulting in a fuel consumption of 8.5l / 100km or 27,7mpg (US) after having drivin 981 kilometers (613 miles). Comparing it to BMW 530d xDrive's I drove before, though they were the sedan (F10), the result is quite comparable. This questions if the method of downsizing really does help fuel efficiency or if it is merely destined to look good on paper.

Previous fuel consumption reports:
And watch the designated playlist on Youtube, that features many more fuel consumption tests on video.

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