Back when I was just out of High School, I was a manager at a Texaco Station. One thing I learned there was that different fuel companies had different standards for purity. Chevron and Texaco were pretty much the top of the list as far as fuel purity. Granted, this was about 12 years ago. This is what I learned from the fuel delivery drivers. When they hauled a load for one of the "budget" fuel companies, they had to flush the tanker trucks because of the layer of sludge and grime on the bottom of the trucks. There is a max levels of impurities allowed by law, and when the "budget" companies would get a dirty batch of fuel, they'd hold it until a cleaner load came through, then blend the batches to meet the maximum level of impurities. The high end brands, on the other hand, prefiltered their fuel before it arrived at the storage yards, then filtered again as it was loaded onto the trucks... And then our pumps had filters as well.
