We've had the discussion on several occasions and he never follows through. He wears the same soiled pants for three days at a time. My house reeks. He has no problem going to church and into the grocery store in this condition. He also refuses to surrender the keys to his car and has had several fender benders this last year and has gone into the store while leaving his car running. He's putting up a huge fight and I don't know how long to continue this battle of the wills.
About the car -- I agree with everyone else. Get those keys away from him before he hurts an innocent person. Reason with him that other people do not owe him their lives or health so that he can drive. Sometimes it helps to ask him how he would feel if he killed a child. If he relents, tell him you will take him where he needs to go and get those keys away.