What Am I Riddles

Question: What has 6 wheels and flies?

Question: What can you smell but not see. And can be deadly, too.

Question: I can run but never walk. Wherever I go, thought are close behind me.

What am I?

Question: Whoever makes it, tells it not. Whoever takes it, knows it not. Whoever knows it, wants it not.

What is it?

Question: I fly, yet I have no wings. I cry, yet I have no eyes. Darkness follows me; lower light I never see.

What am I?