So, to re-iterate, don't buy dirty gas. That is: go to a gas station
that sells lots of gas, is a national brand, is of fairly recent
construction, and one that you think is at least inclined to make
sure every thing is clean.
This is a very good suggestion. Specifically, see if you can find Amoco
Ultimate in your area. This is the best stuff, according to several sources
and my own experience.