While world governments held climate talks in Paris, President Enrique Pena Nieto's office announced USD 3.1 billion to reduce sulfur content in gasoline produced at six refineries of state-run firm Pemex.
The project is to be completed at six refineries in early 2016.
Another USD 3 billion will be spent at three refineries and a gas processing plant so that they can produce their own electricity, cutting 3,000 tonnes of greenhouse gases per megawatts generated each year.
The government will also spend USD 13 billion to increase its capacity to process crude oil and another USD 3.9 billion to reduce the need to import diesel with low sulfur content.
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Pena Nieto is due to announce the investments later today.
The projects will generate 63,000 direct jobs.
Mexico was the first developing country this year to submit targets for the United Nations climate conference, pledging that its greenhouse gas emissions will peak in 2026 before falling.
The 195-nation UN talks have been billed as the last chance to avert the worst consequences of global warming: deadly drought, floods, storms and rising seas that will engulf islands and densely populated coastlines.
To reach an elusive deal by a Friday deadline, however, governments must first resolve a handful of decades-old disputes that have blocked the path to a universal climate pact.
Nations remain divided over providing financing to help developing nations cope with global warming; how far to limit planetary overheating; how to share the burden between rich and poor nations; and how to review progress in slashing greenhouse gases.