(CNN) For many Venezuelans, oil is a birthright in the country blessed with the largest crude reserves in the world. Despite wild hyperinflation, Venezuela's government has never increased the price of gasoline. Today, amid a crushing economic crisis, filling up a tank in Venezuela is still basically free -- but only if you can afford to wait for days in line.

Over the last two weeks, people from several states in Venezuela have described severe gas shortages. It's not the first time that the country has suffered gas shortages, but previous crises were blamed on bad distribution and logistical inefficiency. This time, as citizens find themselves queuing for days at the gas stations, many are starting to fear there simply is not enough oil for all.

Caracas is still fueled by a steady supply, which critics of the embattled President Nicolas Maduro describe as politically motivated favoritism: Keeping the capital well supplied helps prevent further anti-government protests, after months of violent unrest.

But in the western city of San Cristobal del Tachira, Lorena Amaya, 42, spent three days sleeping in her car with her sister, as they waited in line to fill the tank with gas. The two sisters parked their vehicles one in front of the other and placed a mattress in the first one to create a bed.

"Today, it's my son's birthday, and look where am I," she told CNN. She only briefly left the gas queue to visit her 10-year-old son that morning, while her sister held the spot.

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