Hi, I just bought a 06 2.5T S60 with 24K Miles on it. I have only driven the car for 200 Miles, but I am feeling that the engine is a little rough when I accelarate at higher speeds. I can also feel the ride not that smooth on the interstate. I can feel the little ripples from the road through the steering wheel. Does the gas octane make a difference with regard to the engine roughness?Is the bumpy ridenormal with the S60 or should I just take it to the dealer 70 miles away?