Cars Q&A

I am interested in having a SUV, either Safari GX 4x4 or Scorpio 4x4. I wanted to know a> If 4x4 functionality is not used while normal running, will the mileage be still imapacted ( if yes, by how much a liter?) b> I will be driving this car by my own, how comfortatble will it be for co-driver, and rear passangers? c> What is mainteanace cost in comparison to Scorpio. d> Which vehicle is actually meant for 4x4 drive (heard that chasis of Safari is to heavy and may sink in mud/sand) and which one better to operate. e>If I would like to keep this vehicle for next 6 years, which do you suggest is value for money.