The Medium Diesel Engine (MDE) is a four-cylinder diesel engine developed by Adam Opel AG and branded "1.6 CDTI Ecotec" in most markets. Opel also adds the marketing term "Whisper Diesel" in some markets, claiming relatively low levels of noise, vibration, and harshness. Production commenced in late 2013 at Szentgotthárd, Hungary. The MDE is Opel's first all-aluminum diesel engine and offers a power density of 85 hp (63 kW) per liter 136 PS in its most powerful version. Maximum power and torque have been increased versus the previous-generation 1.7-liter engine, while fuel consumption has been reduced by up to 10 percent compared with a 2.0-liter CDTI engine of similar power output. This new 1.6 CDTI engine will replace the current 1.7-liter and lower-powered 2.0-liter diesel engines in a wide range of Opel models, with more- and less-powerful versions to come. The most powerful version of this engine, delivering 136 PS at 3,500–4,000 rpm and 320 N⋅m (236 lb⋅ft) at 2,000 rpm, was first introduced in the 2013 Opel Zafira Tourer, and later in the 2014 Opel Astra J and restyled 2014 Opel Meriva B. In 2014, versions were released with power outputs of 110 and 95 PS.

The Opel Zafira is a car manufactured and marketed across three generations between 1999 and 2019 by Opel. Based on the Opel Astra platform, it is developed to occupy the multi-purpose vehicle (MPV) segment.