I had after market mud flaps - removed them (after I lost a couple) and put OEM. My MPG improved slightly - no idea why. Those OEM flaps look small but they catch a helluva lot of stuff. No drop in MPG
You guys get snow/mud etc right (uhm) Over here, its mainly rain puddles so don't think it will make much of a difference.
Wind visors - make 200% sure to put OEM. The stick on create a lot of wind noise. The OEMs are pricey but they sit so flush its terrific. No extra wind noise.
They are going to be OEM and am used to extra wind noise as I had them on my recently sold 6.
Suggestion: Get a moof roof deflector. OEM only. Again no idea why - but after putting it on my MPG has actually increased. For a commute in summer I averaged around 24 mpg but after putting it on I consistently got around .5 mpg more.
OEM (uhm)