The outcome should confirm the position of the independent Frost Group, which first launched the product in July, that the fuel does not damage engines not adapted to the familiar green unleaded.
The tests have been carried out on the road, and under laboratory conditions, but are unlikely to quell the industry storm the launch has created.
James Frost, chairman of Frost Group, is defiant. "What matters for any petrol is the octane level. It doesn't matter what the lead content is, as long as there is an effective substitute for the lead," he said.
Lined up against him, though, is an impressive array of big names in the motor and petrol retailing business. Shell, Rover, the AA and the Petrol Retailers Association have all come out against the initiative. However, the Asda supermarket chain has begun quietly selling unleaded four star.
Frost itself is already selling the product from more than 100 of its 1,200 stations.
In a further twist, trading standards officers are split over whether the new fuel - which sells from red rather than green pumps - misleads customers into thinking they are buying leaded four star.
The controversy comes at a time of rapid consolidation in the market, where profits are key to survival. Within the next two years, industry watchers believe the number of petrol stations in the country will shrink to 15,000 from 18,000 plus at present.
Shell says its position is that it accepts this type of product should be introduced, but "only after careful consideration, and with proper measures taken to decide how the public should be educated about the product's relative merits".
Mr Frost's reply is: "There is no going back now, only forward. Unleaded petrol has been compulsory in Sweden since 1992, and in Austria since 1989."
Meanwhile, Frost has issued a writ for libel against the Petrol Retailers Association, which declined to comment further.Reuse content