Hi hot mokka,
This is my third vauxhall having previously owned two Zafiras.
The 1st was a 2.0ltr CDTi - t'was a good runner although I started to suffer problems with the engine losing power whem motorway driving so decided to change it.
The 2nd was a 1.9ltr SRi diesel - a big improvement over the previous model with the added benefit of the sports button (tho too tight to use it often). I did notice a change in engine noise when the Zafira was cleaning the diesel particle filter (initially thought there was something seriously wrong but later realised t'was the filter cleaning process).
So onto my Mokka - a much better drive than both Zafira's, however u have to put your foot down in low gear due to the torque levels; aaaaand the noise level of the engine is far more noticeable than my previous Zafiras. This is noticeable in lower gears but I found when motorway driving the engine noise is not that big a deal and barely raises the noise level over the sound of the radio.
All in all the diesel engine is noisy in low gears but improves when travelling on faster roads and in higher gears (i dont mind this as I am used to driving diesels in work too)