The squeeze on Britain's refineries has been underlined by new figures showing that t he UK's second-biggest operator lost money during a tough quarter.
The Stanlow refinery near Ellesmere Port in Cheshire, which supplies about 15% of the UK's petrol and diesel and also makes fuel for jets at Manchester Airport, has been hurt by the glut of petrol stocks across Europe.
An excess of petrol but a shortage of diesel in the UK and Europe, as more consumers switch to driving diesel cars , impacted on Stanlow's margins in th e April to June quarter.
Essar Energy bought Stanlow from oil giant Shell about two years ago, and has been slashing costs and overhauling the site to boost profitability.
Europe's refining industry has been shrinking amid lower fuel consumption and pressure on consumers, companies and producers to cut emissions.
The Coryton refinery in Essex became the UK's highest-profile casualty when it closed last year with hundreds of redundancies after its owner, Petroplus, collapsed. Teesside refinery also ceased production in 2009.
A report by MPs recently said the UK refining industry has not managed to keep pace with global shifts in supply and demand and called for a level playing field on costs and legislation.
Stanlow is the UK's second-biggest oil refinery behind Fawley, near Southampton.
Essar said it is on target for a multimillion-pound upgrade to Stanlow, including extending the life of Europe's largest catalytic cracking unit by 25 years.
In March, a £23 million 450-tonne steel regenerator head was transported to the refinery from Ellesmere Port Docks - forcing the temporary closure of the M53 motorway.
Refining costs exceeded profit margins during the three months to the end of June at Stanlow amid high gasoline stocks and weaker diesel prices relative to petrol - ensuring an unprofitable quarter for the plant.
Gross refining margins at the plant slipped to 4.86 US dollars per barrel (£3.11) during the first quarter from 7.53 US dollars (£4.82) a year earlier. The refinery typically needs to earn a gross margin of around 6 US dollars (£3.84) p er barrel to break even.
Essar has set a new target of Stanlow achieving an average 6 US dollars per barrel gross margin by the end of March 2015 - compared with around 2 US dollars (£1.28) when it bought the plant - to insulate it from "continuing volatility in industry-wide European refining margins".
Stanlow, which has capacity for 75 million barrels per year, earned pre-tax profits of 202.3 million US dollars (£129 million) in the year to the end of March, compared with losses the prior year.
Essar paid 350 million US dollars (£224 million) for Stanlow, which employs about 1,000 staff.
Much of Stanlow's oil is supplied by Shell, but North Sea crude oils now comprise less than a quarter of its raw product, compared with more than 90% in 2011. It sources cheaper fuel from around the globe including Russia, North Africa and offshore Canada.
Stanlow has also switched to using cheaper natural gas in its burners rather than fuel oil.
The plant produced 19.3 million barrels during the first quarter, down on 19.7 million a year earlier.
A spokesman said: "Everything is on track for our major turnaround at the end of this year."
The sprawling Stanlow site traces its roots to 1924 when a small bitumen plant was set up there.