I want to shoot outdoor road videos looking through windshield of car in broad day around noon time moving at about 25 MPH. I want to document what the road and surrounding areas look like for web display which means videos would be downscaled. What is the recommended settings like mode, focal length, shutter, aperture fstop etc?
Shooting through a windshield is a very dicey proposition. There is an amazing amount of glare that you don't see when you are in the car, but which you will see when you look at your camera footage. A far better solution would be to mount a GoPro (or some other small, disposable camera) on the exterior.
Nevertheless, if you insist on using a DSLR, then only with a wide-angle lens will you get "the surrounding areas" to give context to your road. You can think of angle of view this way: if you have a 90 degree field of view, then you have (in the left half of the frame) something that sees the range from 45 degrees left to the center of the road and (in the right half of the frame) something that sees the range from 45 degrees right to the center of the frame. 45 degrees to one side or another is not very wide-angle (compared to turning your head and looking sideways), but wide enough to show some very limited context. To achieve that with a DX format, you need a 10 or 11mm lens.
For shutter speed, you don't want too much blur. 25 miles per hour is 36.7 feet per second. Since you are shooting at max 45 degrees, 36.7 * cos(45) = 26 feet per second. If you shoot at 60 fps with a 180 degree shutter (1/120th of a second), then the largest blur on the sides will be 26/60 = 2.5 inches. 2.5" may be an acceptable amount of blur for a building-sized object that's on the way out of the frame. If you look closer to the center of the frame, say 22.5 degrees off center, the blur will be 36.7 * cos(67.5) = 1.4 inches.
Wide-angle lenses tend to have deep depths of field, so you can safely use an aperture that gives you the right exposure (but check your depth-of-field charts).
But a GoPro will give you a better result for many reasons, not least because they have built-in very wide-angle lenses.