The fuel mileage on my 240 D (1983) drops off fairly significantly in the winter. (From 350 miles per tank to just over 300). I have a new thermostat in the car and it warms up quickly and produces very good heat. I am also using synthetic oil, 5W50 to insure easy cold weather starts. However, I notice driving around that diesel trucks and buses cover their radiator grill in the winter. I assume this is to allow them to operate at a higher temperature and therefore more efficiently. I wonder if this would help my 240D. It would be quite easy to make a cardboard or plastic shield to go behind the grill and in front of the radiator. ( I have had to do this before when my thermostat has gone out.) I remember a friend of mine who had an old Peugeot that came with a vinyl cover for the radiator grill. Surely covering the radiator serves some purpose other than deleting excess radiator space since the diesel trucks and buses all do it and have thermostats. Any thoughts?

Darryn
240D - 130K