I've seen something here in the parking lot at work...late 90s/early 00's Sebring coupe with what looks like an aftermarket bumper cover that has rippled plastic in place of the standard open grille. Not a "grille block" per se but not-so-cleanly blocks the grille none the less. Since it's neither aero-clean due to the horizontal ridges approximating the original grille shape nor a DIY job I don't think the original intent was improved mileage.
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