I have noticed that it does tremble when I get on the freeway (its an uphill climb), but thats coincidentally when I roll the windows up and start the A/C. I just got the oil changed today, and I'm running Mobil 1 Full Synthetic, 0W-20. Haven't had it do it once today, but I only drove it about 3 miles from the shop to work. So I'll have to see when I get the A/C going. Even still, for the car to do that when the A/C is on is just unacceptable....I've owned nothing BUT 4-cylinder cars save for my Chevelle, and NEVER experienced that. Besides, I keep them on the lowest or second to lowest setting.