Just for some context - with a growing family (I must find out what is causing that!) we have a 4 year old Volvo v70 T6. We do not do wax based fuels in our house. It's a big girl, about 1780KG with a 3 litre straight six, light pressure turbo (285bhp) and 4wd. Average consumption in mixed driving - 22mpg. In London last week - 18mpg.
So the Maserati is not really that much worse in the real world and has 100bhp more. Also, think the Gransport may just have the Volvo on road presence and looks.
Damon