I have never had a problem with my Kia Optima. It is very smooth driving and it has great acceleration. Gas mileage is terrific on the highway, but city driving uses much more gas. It is very comfortable for the driver and passengers and there are many accessories that I got with my purchase. I am extremely satisfied with this car, and I highly recommend it to everyone. I would purchase another Kia Optima in the future. I have yet to find anything that I don't like about it.