I claimed the higher rates of both components when my severely autistic son turned 5, at first I was refused, so appealed and was then awarded it for 3 years (you need it at least 5 for a car) I appealed again as friends of mine with children less severe than mine were awarded it for longer periods, and finally got it. The whole process took 18 months and it wasn't backdated. My Mother has Alzheimers and she was refused it (my Dad wont appeal) I think it is truly down to who looks at your form at the time, but if you disagree with a decision please appeal! Good luck