Group C replaced both Group 5 special production cars — such as the Porsche 935 — and Group 6 two-seat racing prototypes, such as the Porsche 936. Its conceptual roots lay in the ACO's GTP category introduced at Le Mans in the mid-1970s, which had limited fuel consumption rather than engine capacity. The FIA applied the same principle to Group C, placing a minimum weight limit of 800 kg on cars and a maximum fuel capacity of 100 litres. With competitors limited to five refuelling stops within a 1,000 kilometre distance, the effective allowance was 600 litres per 1,000 km.
Engines were required to come from a recognised manufacturer with cars homologated in Group A touring cars or Group B GT cars, making the class accessible to major automotive companies. Because no specific engine formula was mandated, a wide variety of approaches could compete: large naturally aspirated engines had a theoretical chance against small turbocharged units, and the endurance emphasis encouraged reliability and efficiency alongside outright speed.
Ford with the C100 and Porsche with the 956 were the first manufacturers to join the series for 1982. Porsche's 956, with its proven flat-six turbocharged boxer engine, quickly established dominance. As the decade progressed, manufacturers including Lancia, Jaguar, Mercedes-Benz, Nissan, Toyota, Mazda, and Aston Martin joined, creating a diverse and competitive grid. Many of these teams also competed in North America's IMSA championship, whose GTP class shared broadly similar regulations and served as a parallel development ground.
By 1989, Group C's popularity was approaching that of Formula One. Cars were reaching over 400 km/h on Le Mans's Mulsanne Straight — the WM-Peugeot recorded 405 km/h in 1988 — and manufacturer investment produced genuinely extraordinary machinery. Group C Junior, introduced for 1983, became Group C2 in 1984, providing a lower-cost entry point for privateer teams using engines such as the BMW M1 unit and Cosworth DFL.
The FIA's attempt to revitalise Group C in 1989 by aligning it with a 3.5-litre Formula One engine formula inadvertently destroyed it. Cars built to the original fuel-consumption formula — such as the Porsche 962, widely raced by privateer teams — were burdened with performance restrictions, while only major manufacturers could afford the new 3.5-litre formula cars. The cost of the new cars was prohibitive for the privateer teams that had provided the backbone of the grid.
The consequent collapse of entry numbers led to the cancellation of the 1993 World Sportscar Championship before the season began, though the ACO allowed Group C cars to compete at Le Mans in 1993 and 1994. A notable coda came when the Dauer 962 Le Mans, essentially a modified Porsche 962 C1 car re-categorised as a road-legal GT, won the 1994 Le Mans. The 962 was subsequently banned, and by 1994 Group C had effectively ceased to exist at the highest level of international competition.
The era produced iconic machinery including the Porsche 956 and 962, Jaguar XJR-9 and XJR-14, Mercedes-Benz C9 and C11, Toyota TS010, Nissan R89C and R90CK, and the Mazda 787B — the latter winning Le Mans in 1991 as the only rotary-engined car ever to take the overall victory. The regulations accommodated both turbocharged and naturally aspirated engines, diesel experiments, and innovative aerodynamic concepts, making Group C a genuine laboratory for automotive engineering.
Group C produced some of the most technically advanced and fastest endurance racing cars built under production-related regulations. Its fuel-consumption formula forced teams to pursue efficiency as well as power, prefiguring the energy-based regulations that would return with the LMP1-H era decades later. The period is widely regarded as a high point of manufacturer involvement in endurance racing, producing fierce rivalries between Porsche, Jaguar, Mercedes-Benz, Nissan, and Toyota that generated both engineering innovation and a passionate global audience. Group C cars remain prized historically and continue to race in specialist historic motorsport events.