I am not sure if they still do it but Exxon use to have a red dye additive. In at least carbureted cars the dye would eventually clog the carb. Had this happen on my old Mazda pickup. Ever sense then staid away from Exxon. Not sure if it still relevant.
By the way gas is gas. It is shipped in pipe lines and all mixed together from the different manufactures. The difference is in the additives.
Rich S
