Alright here is my best advice even though I am no expert. I have met autistic kids and worked with them,and also my dad deals with autistic kids because of his job. There are many types of autism, some are so severe that they must be put in a special school while others are mild and can go through school and college. I have dated someone who had asburger's syndrom which is a small type of autsism. I know the symptoms can be naiveness, and some social situation and problems. It really depends, I think sometimes it affects with what you said, not being able to tell the difference between a joke and not a joke. He might be mixed with OCD also, but autistic kids go into their own little world have the time. I would say alot of times they have a one track mind. Example: talking about cars, what you said. They have a special interest and a special talent that they are drawn too. You really can't change him because this is what they were diagnosed with so I assume if you want to be his friend you just have to have the patience and know these facts, and remember they can't help it.