We drove the 6-9 mile (the road sign said the latter; my odometer the former) in my 1989 Chevrolet Astro minivan. I'm not sure why some people seem to think you need some sort of monster truck to make the drive. Just slow down over the washboard sections of road. We spent an hour at the crater, and it's a seriously impressive site. If you like impressive geology, and not just in the crater but the surrounding landscape, you'll enjoy this.