Are you sure your plug is oil fouled? Grey smoke would be more a fuel issue. Running way too rich. You may want someone with an SDS to go into the engine fuel management and see what type of fuel it's set up for. I've seen these switch on their own to E85 causing a extremely rich condition, flooding one or more cylinders that result in low or no compression. I think that there may even be a software update for this. If that's the case, reset the values for the fuel system, change the plugs and run until it clears. I may be way off base, but like I said, I've seen this a few times when the customer was ready to throw the car away when it was an easy fix. Although, everything that I just mentioned wouldn't explain the high oil consumption. So, I could be wrong.