basjoos (v.) - to make aerodynamic optimizations at a micro (vs. macro) level.
(OK, yes, obviously basjoos does macro too, but whenever I start nitpicking about some small aero detail, I instantly think about his silicone-filled panel gaps. The "basjoosed panel gaps".)
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So, no, I don't have any pics to post yet, but today I bought a roll of 3 mm (about 1/8) thick peel 'n' stick weatherstrip because I was looking for a quick 'n' clean aeromod project to do before my next big one.
I fit the foam strip in the gap all around the driver's side headlight assembly. (I'll do the other side tomorrow.)
That gap ultimately leads into the engine compartment and under the car, so despite it being a small area, it's pretty much the top of the list in terms of where I don't want air to go unnecessarily.
I calculated a total open area of 43.2 cm2 around both lights, or 6.7 square inches.
Inconsequential? Mercedes didn't think so ("sealed joints on headlights"):
From thread:
Mercedes modded C-class: Cd 0.25. Up 7.5 mpg over regular model (with other mods).