I too had an issue with tire vibration as soon as I took the car on its first highway trip. The vibration began at 70 miles per hour. Strangely, it did not get worse as speed increased as one might expect with a typical tire or balance problem. The dealer replaced two of the Michelins with new Michelins - telling me the problem related to "flat spots" on the tires. The vibration has disapeared, but I am skeptical of the explanation provided by the dealer in light of all I have read in this forum.
Other than the vibration issue, which is solved for now, the car is phenomenal. I have previously owned a Lexus and several Chrysler LHS'. None of those vehicles hold a candle to the balance of sport and luxury Cadillac has achieved with the Seville.
Just bought a previously owned SLS with 34k miles on it and took it up to Sacramento from San Diego. Wonder of wonders, on one tank of gas, averaged 70mph with the a/c running all the way and averaged 29.2mpg.
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