ADNOC is lining up bankers to work on a potential offer for MFG, which has been put up for sale with a price tag of about £5bn.
City sources said that ADNOC, which is among the 20 biggest oil companies in the world, had yet to make a firm decision about whether to bid ahead of an initial deadline. However, it is preparing to hire JP Morgan, the Wall Street investment bank, to advise it on its interest in the UK company, they said.
ADNOC would be a significant player in a bidding war for a company that has rapidly grown is estate and profitability, and is now seeking to harness the automotive industry's efforts to embrace the transition to cleaner energy.
MFG has committed to spending £50m this year on installing hundreds of electric vehicle charging points across its roughly-900 sites, and believes it can play a leading role in that shift during the coming years.
A bid from ADNOC would represent one of the biggest single investments by a company from the Gulf state in a British business, and follows the signing of a £10bn sovereign investment partnership between the UK and UAE last year.
Technology, energy transition, infrastructure and life sciences were identified as the principal focuses for the partnership between the Abu Dhabi fund Mubadala and the UK's Office for Investment.
ADNOC produces roughly 3m barrels of oil each day, as well as 10.5bn cubic feet of gas, placing it among the world's largest producers of the two energy sources.
If it does bid for MFG, it will probably be pitted against Fortress Investment Group and Macquarie, the Australian financial services behemoth which recently bought Roadchef, the motorway services operator, for about £1bn.
People close to the process cautioned, however, that a sale was not certain to go ahead, given difficult financing markets. Clayton Dubilier & Rice (CD&R) will only proceed with a sale if it can secure an attractive valuation, they added.
MFG has grown through a series of acquisitions to become the largest independent player in the sector, behind BP and Shell.
A merger of its assets with Morrisons' petrol stations was mooted by City analysts at the time of the supermarket chain's takeover by CD&R, but the prospect of that transaction receded after a £750m deal for EG Group to buy Asda's forecourts was abandoned in October.
Asda and EG Group are both controlled by TDR Capital and the lagger's founders, Mohsin and Zuber Issa. CD&R has owned MFG since 2015, and has now picked a quartet of banks to oversee the company's sale.
Citi, Deutsche Bank, Goldman Sachs and Royal Bank of Canada will work jointly on the process, with a stock market listing considered to be far less likely.
The company has grown substantially since CD&R bought it in 2015 from Patron Capital Partners in a deal worth about £500m. Three years later, it paid £1.2bn to add MRH, the market leader, creating a group operating under fuel brands such as BP, Esso, Shell and Texaco.
Profits are understood to have risen about tenfold since CD&R's original acquisition of MFG.
Like rivals, it has invested heavily in its convenience retailing proposition, featuring the likes of Costa Coffee, Greggs and Subway at many of its sites.
EG is undertaking a review of its strategic options and has been linked with a merger with Canada's Alimentation Couche-Tard, while Rontec, the group controlled by the entrepreneur Gerald Ronson, has also been periodically linked with a sale.
MFG is run by William Bannister, who acquired the business in 2011 through a management buy-in, while it is chaired by Alasdair Locke, a serial entrepreneur in the energy industry.
Both men would be in line for substantial windfalls from a £5bn sale. ADNOC could not be reached for comment on Friday, while JP Morgan and CD&R both declined to comment.