Same here, went to get the cruise control wiring replaced and they pulled the black cps, and broke it into pieces, then gave me a pos grey one.....Which just left me stranded on the road.If you are going from a GOOD working black CPS to a grey then I would say likely a mileage decrease. Now if the CPS was having issues then anything is possible. But most of the people I know that got suckered into a grey from a good black all lost mpg. I lost about 2 mpg back when my X was totally stock from the swap they did without my permission when it was in for a different recall. Even had told them not to touch ANYTHING else. Get a black on if at all possible IMO.