I was talking to this guy that makes biodiesel. He said he gets used veg oil and filters it several times and then adds kerosene and gasoline to it. I would like to know if he was telling me correct info. I always thought gasoline and diesel engines don't mix.

That is NOT Biodiesel. What he is doing is called blending and it's very different than BIO. Have a read.

http://biodiesel.infopop.cc/eve/forums?a=search&reqWords=blending