[Piwoslaw]

Here is how I partially blocked the lower grille:

Just a piece of plastic tucked under the license plate, covering the open part of the grille.
It open on the sides, so that the fan can suck in air, should the engine get too warm:


Today I got access to a garage, so I got under the car, cleaned the oil pan, and put a 3mm layer of foam insulation on it. Hopefully this will prevent some heat loss, as the oil pan is dangling in the airstream with no belly pan.