Atlantic Richfield Company (ARCO,) ARCO Oil and Gas, etc. etc. was bought
out by BP in (2000?) The ARCO brand was so strong at the time (and remains
so,) that they kept it alive in the west coast (possibly in other areas, I
don't recall.) They purchased AMOCO at the same time. Just an
FYI......also, I'm pretty sure all gasoline is created equal, until the
additives enter the equation. Most of these are unique to each individual
company. I work in the natural gas industry, for BP, but have never been
involved in refinery work, so I don't have any specifics to share regarding
gasoline production.
I have never been loyal to any particular brand and believe that 'bad gas'
is more commonly a  mis-diagnosis and when it is correctly diagnosed as bad
gas, it is the fault of the station operator, whether intentional or not.
Miguel