[*] purchasing timeframe not specified.
Ref the 5 series my last experience was 1992 in a ‘J’ reg 520. That was so quiet I could not work out what was wrong with it when overtaking an XR2 as the engine seemed to cut out. It was off the clock at 7k rpm. Hadn’t noticed.
I shouldn’t worry too much about a quiet petrol, whatever you get will be powered by a “Mr Fusion”