ALCOHOL FREE AUTOGAS???

[MICHAEL A HARRISON]

Hello, my name is mike (N99476), and would like to start mixing in some autofuel with avgas.  My 415c is approved and converted to support this.  My question is how do I insure that the autofuel is alcohol - free?  Is there a particular brand of fuel that is recommended?  Or any that should be avoided? thanks for any and all help