I have experienced "bad gas" twice. The easiest cure is to put a bottle of Octane Boost in the gas tank. This will allow your car to perform "normally" again instead of running the car long enough to refill with "good gas".
I use Shell, Mobil, or Speedway gas stations with good success.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles