When global engineering firms told the Mexican government that building a new refinery according to the country’s budget and timeline would be impossible, President Andrés Manuel López Obrador refused to accept their verdict.

Instead, the president said Thursday that the state-owned oil company, Pemex, and the Energy Ministry, would take charge of the project. He promised that the new refinery, which represents his bid to achieve energy self-sufficiency in Mexico, would cost no more than $8 billion and be ready by 2022.

The decision to reject the engineering firms and press on with a grand infrastructure project reflects a pattern in Mr. López Obrador’s governance, less than six months into his presidency. Told that a plan he envisions can’t be done, he sticks fast and orders officials to turn his ideas into reality.

One of his first actions as president was to cancel the construction of a new airport for Mexico City. Instead, he proposed to build a second airport to complement the capital’s existing one, although studies on the viability of increasing flights through the shared airspace have not been completed.