Indian Oil Corporation is one of India's 7 maharatna companies. It is India's largest commercial enterprises. It accounts nearly half of India’s petroleum market. It has around 9 refineries.

IOCL is one of the Oil Manufacturing company and Maharatna with a very wide marketing network.
The minimum qualification for entry into R&D centre is M.Tech or Ph.D. The scope for Chemical engineers, doctorate in chemistry and Mechanical engineers is more. The basic requirement for job in Marketing, Refineries and pipelines is degree in engineering.

For more information about IOCL and its recruitment, you can go through the below article -

IOCL announces recruitment of Engineers, Officers through GATE 2017

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Indian Oil Corporation (IndianOil) is an Indian petrochemical company. It is the largest commercial enterprise in the country, with a net profit of 19,106 crore (USD 2,848 million) for the financial year 2016–17. It is the leading Indian Corporate in Fortune's prestigious ‘Global 500’ listing of world's largest corporates at 168th position for the year 2017, and has a 33,000 strong workforce. IndianOil's business interests overlap the entire hydrocarbon value-chain, including refining, pipeline transportation, marketing of petroleum products, exploration and production of crude oil, natural gas and petrochemicals. Also, IndianOil has ventured into alternative energy and globalisation of downstream operations. With subsidiaries in Sri Lanka, Mauritius and the UAE, IndianOil is scouting for new business opportunities in the energy markets across Asia and Africa. It has also formed about 20 joint ventures with reputed business partners from India and abroad to pursue diverse business interests. Indian Oil has its R&D Centre located in Faridabad, Delhi NCR