Initially yes, but when you are on a highway, for a long run, going 65 MPH it's like having a 6th gear.
I compared the speed offset, with satellite navigation speed, with stock tires it use to be dead on, now is 3 miles over.
these tires are curved at the edges for low drag. Theory is one thing, this needs to be tested, so once snow is gone, I am taking my CTS for a long test run. Not to mention these are relatively lightweight rims. Performance and Appearance package 18" version does not have the same diameter as my tires, I have a higher wall height.