I almost traded in my brand new 2012 honda civic sedan lx with manual trans!
I was getting a disturbing vibration when I accelerated to about 50 mph.
The whole car vibrated like I was driving over a grooved highway, and then I thought that perhaps I blew a tire or something.
It was intermittent.
The Service Tech discovered that when you have only the rear windows down halfway the vibration happens and sounds like a helicopter!
An aerodynamic thing.
I wanted to let people know this just in case they are experiencing the same issue!
Now that I know it is nothing serious I am back to LOVING MY NEW CIVIC!!!
Getting 30 mpg with mixed around town and highway driving!
Smooth ride, comfortable seats, easy for my dog to get in and out of, big trunk, back seats fold down, easy shifting, good visibiliy, great gas mileage!
I had to get used to not being able to judge the front end because of the steeply sloped hood, but no worries now!