In my humble opinion. It's not the quality of the fuel being dumped into the station's tanks. It's the tanks themselves. Remember way back when? A station's fuel storage tanks were above ground. The EPA required everyone to put them below ground level. Have you ever seen anyone sweeping the area around the fill ports? Yeah, the ports are slightly elevated, surrounded by a concrete skirt, above the asphalt or dirt. But that doesn't stop detritus and water from entering. Snow and ice accumulation. It melts and enters the ports. When a tanker arrives to replenish the tanks, it dumps straight into the tank, stirring up all of that crap and water on the bottom. If you are refueling at that time, it's all going straight into your tank. Don't blame the fuel. Has anyone ever seen a station employee changing filters in the pumps? Do blame the station owner for not keeping the final delivery point clean.