I have only had one bad experience at a Pemex in Mexico. South of Cancun by Puerto Aventuras several guys came running over as we pulled up to the pump. They swarmed us washing windows etc. I made the mistake of opening the gas fill door before I got out - one guy was sort of blocking the door. By the time I got out the numbers on the pump seemed quite high - they filled it up and I could see the liters and charges on the pump. Problem is they were so dumb they had run it up to higher than what our tank can hold. They had not erased the numbers from the previous customer by closing out the pump. So they just kept adding. I argued with them and said there is no way my tank holds that much. The leader asked how much I thought the tank was going to take and how much I thought I should pay. I told him and he said OK because he knew I was going to throw a fit and he and his partners in crime could get fired. In years of travel in Mexico that is the only one time any kind of scam was attempted at a Pemex. But I do watch and I do not open the gas fill door until I am out of the car and looked at the zeros. Counting out the payment bills one at a time also helps. You just have to pay attention in case of that very rare occasion someone thinks they can pull the wool over your eyes.