the octane level has always been a question here as to what is advertised and actuality! since the new gas companies have entered, Arco, Chevron, Gulf i have noticed better fuel efficiency with me using Arco gas! ALL PEMEX gas used in all the northern Mexican states is refined in the USA! the main difference using NOB brands is the consistency of the octane level and the use of ADDITIVES!!!
Funny how efficiency increases when you start getting legitimate quantities, instead of what most Pemex stations deliver.