Hopefully I'm not reposting this, but I think this is new with the 72 kW "urban Supercharger" announcement.
Based on Tesla's map, it looks like the 2018 additions/changes are:
Novi
Detroit
Swartz Creek (near Flint)
Claire
Mackinaw City
Gaylord (Grayling for 2017 seems to have been removed)
Escanaba (U.P.)
Find Us | Tesla
Based on Tesla's map, it looks like the 2018 additions/changes are:
Novi
Detroit
Swartz Creek (near Flint)
Claire
Mackinaw City
Gaylord (Grayling for 2017 seems to have been removed)
Escanaba (U.P.)
Find Us | Tesla