InARush

I bought a used 2013 MKZ EcoBoost AWD fully loaded on Monday with 10,000 miles, and have driven it about 300 miles. A lot of bells and whistles to learn about. Getting 31 mpg mostly highway at about 65 mph. Only issue I have noticed so far, that I didn't notice at the dealer is the blackened exhaust tips, which seem to be stained black from soot. Anybody found a way to clean these and keep them clean? Traded in a 2010 Milan, what a world of difference.