The real pressure comes in the form of political embarrassment to the PRI by the PRD. Continuous, never-ending public jabbing. Pollution in the Big Enchilada is horrible in the winter. Stage ! and Stage II smog alerts, driving restrictions and factory shutdowns.
I have gnus for some of you. It is DF MANDATED that public transportation use only ULSD in new vehicles. This means buses. Municipal not corporate owned transportation buses. So, no new municipal buses. The old ones are falling apart.
The pressure on Pemex is more than is apparent on the surface. Again I can only wish that Mexican newspapers are more widely read here...