fuel

I am a first timer. Just bought a 2012 X5 and wonder about the fuel. In general, does anyone know anything about the gasoline sold at Costco or Walmart? Is it of the quality to use in an X5. The manual warns against "poor quality fuel" that is not of "recognized high quality" and cautions you to use a "top tier detergent" fuel. Does this include fuel sold at these big box stores?

Thanx