John Wyer Automotive Engineering, based in Slough, England, had built the Mirage racing car family from 1967 onward, initially as a development of the Ford GT40 and subsequently through a series of independent designs. The team's association with Gulf Oil Corporation produced one of motorsport's most iconic livery combinations — the powder blue and marigold colours introduced on the very first Mirage M1 — and delivered Gulf's first race wins. During the 1970 and 1971 seasons, JWAE raced the Porsche 917 under Gulf sponsorship, scoring major victories.
When the FIA banned the large-capacity Group 5 cars — most notably the Porsche 917 and Ferrari 512 — at the end of 1971, JWAE commissioned designer Len Bailey, who had previously contributed to the M1, to design a new car for the 3-litre formula.
The M6 featured a steel-reinforced riveted aluminium chassis paired with a detuned 3-litre Ford Cosworth DFV Formula 1 engine mounted as a stressed chassis member — a design approach borrowed directly from contemporary Formula 1 practice. Open fibreglass bodywork with a prominent rear wing completed the package. The first M6 chassis was completed in March 1972 and raced immediately at the 12 Hours of Sebring. A second car was finished partway through the season; a third chassis was built specifically to test a Weslake V12 engine as a potential alternative to the Cosworth.
A closed coupé variant, the M6 Coupé, was developed for the 1973 24 Hours of Le Mans. This low-drag version used the 2,995 cc Ford-Weslake V12 engine rather than the Cosworth DFV. Testing, however, produced lap times approximately 16 seconds slower than the open M6 with the Cosworth, ending that particular development thread before it reached the race.
The M6's competitive record was modest. The car's primary victory came at the 1973 Spa-Francorchamps 1,000 km, the same circuit where JWAE and Mirage had first won in 1967. Beyond that single win, the 1973 season was largely disappointing. The Weslake V12 programme consumed significant resources but ultimately proved no better than the Cosworth DFV, whose strong vibrations caused persistent reliability issues throughout both seasons.
The Cosworth's vibration problems were a recurring theme during the M6's competition life. While the engine was a proven racing unit — the foundation of virtually all Formula 1 success of the era — its high-frequency characteristics placed unusual stress on a sports car's drivetrain and ancillaries, contributing to retirements at key events.
Following the M6 programme, four of the five M6 chassis were rebuilt as GR7s. The GR7 was renamed Gulf GR7 for 1974, more overtly acknowledging Gulf Oil's sponsorship, and the revised car placed second in the 1974 World Championship for Makes.
The GR7 programme then led directly to the team's greatest achievement: the GR8, powered by a Cosworth DFV and driven by Jacky Ickx and Derek Bell, won the 1975 24 Hours of Le Mans outright. A second GR8 finished third in the same race. The 1975 Le Mans victory was the culmination of the entire Mirage project begun in 1967 — and the last overall Le Mans win achieved under Gulf Oil sponsorship.
The M6 occupies an important transitional position in JWAE's history, bridging the dominant Porsche 917 years and the eventual Le Mans triumph with the GR8. In itself, a second-season car with a single race win, it demonstrated the difficulty of adapting a Formula 1 engine — the DFV — to the demands of long-distance sports car racing, a problem that would influence the GR7 and GR8 development cycles and ultimately be resolved through refinement rather than by abandoning the basic architecture. The M6's aluminium stressed-member chassis philosophy established the template that carried the Mirage programme to its 1975 pinnacle.