No its not. I used to sniff petroleum before they made it unleaded and it only kills brain cells. You might end up with some burns though as gasoline that still contains lead [can you still get that]? tends to burn your skin with prolonged contact. I used to have to put petrol in a steel cup, put that in a bag and then inhale the fumes as the petrol just burnt through plastic bags.
The only thing that might happen is you suffocate or drown, neither of which would be pleasant if [big IF] they were to happen.