Well if your car commute is two hours then you are getting four hours of exercise for two hours of your time. Anyway, two hours for 60 miles comes out to 30 mph average speed. Is this even throughout the route or is there one half that is much slower than the other. If so, you might be able drive the fast stretch and then bike the slow stretch and the biking won't cost you any net time at all and you will be getting the exercise. In this case you would be crazy not to bike commute at least the slow stretch.