Viva Energy, one of Australia's largest energy companies, has been fined $100,000 for an oil spill in Sydney Harbour that took more than six months to clean up and was described by a judge as "foreseeable".

The company will also be required to publish an admission it was "unaware of, and has been unable to locate records of, any inspections, testing or maintenance work" on the corroded pipeline that leaked on December 30, 2016.

The leak, at the Gore Bay fuel storage, resulted in about 800 litres of fuel oil spilling onto nearby land, with about 500 litres of that entering the waters at Gore Cove, near Greenwich, according to the judgement handed down by Justice Tim Moore in the Land and Environment Court on Friday.

The spill affected about 350 metres of the nearby shoreline, an area that supported "an assemblage of intertidal organisms, including whelks, limpets, crabs, sea snails and barnacles, along with various types of algae", and fish habitat, the court found. The impact on aquatic life was of "moderate significance".