I use Chevron and twice I've had a problem with fuel. I've isolated it to one particular Chevron station so I avoid it. What's funny is this station is on a main thoroughfare in the Phoenix area and does a lot of business.
I use Chevron because it has Techron in it. BMW used to package Techron under their own brand name and Mercedes dealers would add a bottle of this stuff when they serviced my wife's 190D.
When we recently had a gas shortage in the Phoenix area, I discovered that all the gas sold in the Valley comes over two pipe lines. This is the so-called Phoenix gas that's supposed to reduce emissions. I got to wondering how various brands could be different if it all came from the same source.
I sent a note to Chevron and they told me they put the additives in at the tank farm when they fill their delivery trucks. I'm not sure I buy that but that's their story and they're sticking to it