My car had 40K miles on it when it got a rough idle while stopped at stoplights. The Buick dealership tried to claim it was because of AC system and I promptly informed them this had been happening during the winter when the AC was off. In addition, it would not matter if the AC system was on or not it should not be idling rough. After having them check it they cannot figure out what the issue is and cannot give me a solution to the issue. My moms car with 250K miles and over 11 years old runs better than my vehicle that has had all required maintenance done.