Few months ago, I had to remove the (cardboard) lower grill block because megane had a problem at the radiator. After the repair I did a coroplast upper grill block.
The 1st version of the new upper grill block prevented anybody to open the hood, so I had to make a 2nd version to permit to change the oil (changed last week from 5W40 to 5W30). The 1st version was conceived by 1 single part so the Renault emblem and the hole between it and the bumper were hidden. The 2nd one is simply the first one without the central part.
Here are 2 pictures of the 2nd version :
To make the engine hot quicker, or to keep the engine hot longer, the upper grill block seams to be as effective as the lower grill block.
Only recently I remarked that above 80 km/h I'm hearing the wiper blades. I remarked it by the fact the noise disappeared when I removed the wiper blades in the hope to have a better Cd. I think this can be explained by the fact that more air is pushed over the hood.
Denis.