We have only been taken on the Pump irregularity once that I know for certain on Diesel.The Pemex on the Western side of 15 South of Los Mochis!
Gas however was another story entirely!
Once in Todos Santos Our Buddy filled his 22.5 Litre Jerry Can with 30 Litres of Gas.Yes the Tank is Marked and no it wasnt Warm or Overfilled past the Safe Line!
It isn't only in Mexico that this sort of thing happens!
One of Our local Fuel Stations in Port Alberni,BC Canada( Name available by PM) did the exact same thing to Me on Marine Gas 2 Years ago. I will never darken their Doors again!