HFO definitions

Hfo

1) Heavy fuel oil
Found on https://www.crosswordclues.com/clue/hfo

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Hfo

heavy fuel oil
Found on http://www.encyclo.co.uk/local/20100

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HFO

Heavy fuel oil (also called residual fuel oil, RFO)
Found on http://www.encyclo.co.uk/local/20824

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