I've posted before, but since you asked....
For years and years I kept going back to Esso (91 or 92 depending on which year you ask me). Other brands I usually try are Sunoco 92 and Shell V-Power 91/92 (depending on which year).
I first started comparing fuel for my Porsche 968 I had from 2000-2005. It called for 93 AKI fuel but would run on "as low as" 91 IIRC. The only brand meeting that on the sticker was Sunoco 94 but I found that Esso (92 in those days) could also run fine without retarding the timing. Everything else caused knock-then-retard. It's off topic, but in 5 years of ownership I think I only ever got *3* great tanks of gas. As soon as I started the car and pulled away I could tell I got a good one. Smoother idle, significantly increased power (like, it briefly scared me once it was so much faster) and substantial increase in fuel economy (like 30% - the tank seemed to last forever). Next fill up at the same station, back to the "same old" right after re-starting
. I expect perhaps I was experiencing tanks with no ethanol, MTBE or whatever other [censored] they're putting in there other than gasoline to hit 94 AKI. In the 9 years I've been driving my current 1998 BMW I've had one extraordinary tank of gas from an Esso in Grand Bend. Both my friend and I noticed that fill up lasting a lot longer than normal.
Back to the topic. I kept coming back to Esso in my BMW because I found that between those three brands in my area I would usually get either good performance, or good fuel economy, or neither, but Esso consistently gave me both.
Often in the winter I use Shell because I like the Shell carwash better than the Esso one and I like the fill up discount. This winter I had new snow tires but I noticed that I didn't get a substantial fuel economy drop off that I usually see. As a matter of fact I noticed better fuel economy this winter on my new snows (Hakkapeliitta RSi) than I usually get in the summer (Michelin PS2).
I stuck with Shell all winter and never switched back in the spring. It seems that I'm no longer seeing the drop in either performance or fuel economy that I used to see with whatever their new formula is. The 0% ethanol is nice, but in the past it didn't seem to save V-Power from still losing in terms of economy or performance.
I did fill up at an Esso on holidays (only brand in town) and I was mixing it with a half tank of V-Power but I thought maybe there was some better performance after the switch. Maybe I'll have to try a tank of Esso next time again and see.
People used to bash Esso for high sulphur. Since that became regulated I don't think it's an issue any more and, in some ways, the lubricity of some sulphur might be good if it weren't for the pesky SO2 in the exhaust and H2SO4 formed in the oil.