This was one of the first things I got done on my 2013 Volt ... I use my Volt mostly for local commutes, and love rolling the windows down when the weather is pleasant.
My dealer warned that my mileage could go down by up to 15% but the work was done free of charge (it is covered under 3 year B2B warranty). Any reduced mileage fears were unfounded. My local EV range did not change at all. And on a 400 mile road trip with speeds going up to 80mph and averaging over 50mph, I got 42mpg in gasoline only mode, and over 45 miles on a full charge -- both better than EPA.
My dealer warned that my mileage could go down by up to 15% but the work was done free of charge (it is covered under 3 year B2B warranty). Any reduced mileage fears were unfounded. My local EV range did not change at all. And on a 400 mile road trip with speeds going up to 80mph and averaging over 50mph, I got 42mpg in gasoline only mode, and over 45 miles on a full charge -- both better than EPA.