But the company -- PetrÃ³leos Mexicanos, or Pemex -- is not aging well, and it is fast eroding into a creaking, crippled behemoth that even its biggest defenders say must change to survive.  In a once-unthinkable move, President Felipe CalderÃ³n urged an overhaul of Pemex earlier this month, calling on the Mexican Congress to allow the company more freedom to sign contracts with foreign firms better equipped to build efficient refineries and conduct expensive deep-water drilling.  But the proposal -- being touted by its supporters as one of the most important economic reforms in recent Mexican history -- has drawn fierce resistance from a determined coalition of left-leaning opposition parties for whom outsider involvement in Pemex is anathema. They seized control of the Mexican congressional building for more than two weeks this month, with some members spending nights on the floor and leading rowdy protests during the day.  "This is the inheritance of my grandfather, this is our company, and we're not going to let them take it away from us," Congressman Alejandro SÃ¡nchez Camacho, of the opposition Democratic Revolutionary Party, or PRD, said in an interview.  The fight has major implications for the United States, which counts Mexico as one of its four largest foreign oil suppliers, along with Canada, Saudi Arabia and Venezuela. Here in Mexico, the titanic political battle could paralyze the government for months.  Mexico nationalized its oil industry in the late 1930s, seizing control of British and U.S. companies as part of a movement to bring large industries under state control. For decades, Mexicans bragged that their grandmothers had donated jewelry to help pay for the takeover.  The movement toward nationalization, though, has been steadily reversed. The government privatized its national telephone and railroad companies, and last year it sold off the state-run airline, AeromÃ©xico, at a price that CalderÃ³n's critics asserted was far too low.  Pemex has been untouched, in large part because of its extraordinary financial importance. Under the constitution, the company must turn over most of its revenue to the federal government, which relies on Pemex for 40 percent of its annual budget. After paying its huge tax obligation, Pemex must also pay salaries and pensions to members of the enormously powerful oil workers union.  The company has grown exponentially and generated more than $100 billion in revenue last year. But things have soured this year, with production dropping 8 percent and exports falling 12 percent in the first quarter compared with the comparable period a year earlier. At the Cantarell oil field in the Gulf of Campeche -- which was discovered in the 1970s and is frequently ranked as the second- or third-largest oil field in the world -- daily production has plummeted from 2 million barrels a day in recent years to 1.1 million.  The drop-off will almost surely accelerate in coming years, according to David Shields, an independent, Mexico City-based analyst and consultant. CalderÃ³n's energy officials have estimated that Mexico could run out of oil in nine years if major new fields are not found.  In the meantime, Pemex seems to be deteriorating fast. Its pipelines are in abominable condition, leaking profits daily, and its reserves are drying up. Pemex is by far Latin America's largest company -- and the 34th-biggest revenue-generating firm in the world. Despite the huge run-up in global oil prices, it is deep in debt.
MEXICO CITY -- Mexico's giant state-run oil company was once a source of universal pride here. Ballads were sung in its honor, and the money gushed as much as the crude.