Yes, I have been in the oil and gas industry my entire adult life, and I agree. While almost all US gasoline is decent, Chevron gas with Techron really IS the BEST. And low-octane Mexican gas, often contaminated with water due to poor storage conditions, is the WORST.
One of my workers drove his newer Toyota down to Mexico last year. He said the gas made it run like $h!t.
You are absolutely correct. Back in the early 80’s we went down to Mexico to run the Baja 500 race. Decided to just get Mexican premium and add octane booster. Ha, ha. The morning of the race some smart ass in our crew read the rule book which stated any fuel with additives would need to be checked by the organizers. Had them check it and it was 82 octane, AFTER WE HAD ADDED THE BOOSTER!!!!!