The window shade things add drag.
If you're in a cold place, you can take foam pipe insulation and stuff it into the front grille. This will help the engine warm up faster, and retain that heat better. Warm engine = efficient engine.
Your car is already one of the most aerodynamic cars out there. It'll take something major to really improve on that. More effective would be to adjust the "nut behind the wheel" - driving technique.
I'm getting mid-50's in a 12-year-old car with no major mods. Grille block, tire pressure, and a Scangauge. You already have a built-in gauge on yours.
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