Some reason post was deleted.
Additives are added at the terminal for each brand. About 80+% of the stations get their fuel from this terminal, since it is rural, there are two large oil companies that have most of the brand distribution, plus their own no-brand. Each brand gets its additive pack. Services Sunoco, Mobil, Citgo, and no-brand.
Sunoco and Mobil have much higher than EPA additive levels, Citgo and no-brand do not.
There are sprinklings of spillover brands like Hess and Gulf that have one station in a 50-mi radius. These get their gasoline from company terminals in Syracuse, 90 mi away.
Kwik-Fill (United Refining) owns its refinery in Bradford, PA (old Kendall/Keystone) and does its own deliveries in branded trucks to its stations, which are all over Western NY and PA. It has EPA level additives. Around here it does not deliver to other brands, but does elsewhere.
The prior company I used to work for had a fleet of Chevrolet Astos for delivery. They used Citgo only and it carboned up on all of them around 100k. Fuel system cleaning became a regular occurance.
People in the sports car club use high additive fuel and run 100k, 200k, with limited carbon issues.
It is really simple;
1. get high additive fuel and rarely put in fuel cleaners or
2. go anywhere and and add Techron,etc. twice a year.