Hello. I have recently purchased a 2009 W212 CDI BlueEfficiency (145,000 miles) with the engine, OM651 - my first ever diesel - and noticed that it is a bit on the loud side in terms of engine noise. Having come from a silent Lexus IS250 (Petrol), it sounds like a 'bag of spanners' - even when warm. Any suggestions on how to make it quieter? I looked it up and saw that 2-stroke oil added into the fuel filler cap can help (alongside diesel) - is this safe? If not, what else could I do? Cheers!