It's no secret that stars change their names in order to make themselves more marketable.
Now I don't know what Vin Diesel's real name is, but I'm pretty it doesn't say "Diesel" on his birth certificate. Unless he comes from a long and proud lineage of Peterbilt trucks.
It turns out that some of the less octane-related Hollywood names are also completely made up for the sake of standing out to casting directors. It shouldn't come as a surprise in such a competitive line of work, but people are always floored when they find out one of their favorite stars has been living under a pseudonym for most of their lives.