FWIW I tried on a set of 16" aluminum rims originally from an '97 Grand Prix and had no clearance issues and didn't need any spacer. I also tried on a set of 16"s from my old '98 Buick Riviera and they fit without clearance problems. I have a 2013 Volt. I could see how a rim that doesn't have enough offset could have a clearance problem with the caliper, so the answer is 'it depends'. I have access to a couple '04 Grand Prixs, one with aluminum wheels and one with steelies, both 16". I'll have to give them a try.
DDs 2013 Jet Black Volt, '08 VW Passat Wagon 2.0T
Toys '73 Buick LeSabre 455, '54 MG TF