Group C was the race-car formula that encouraged fuel efficiency at Le Mans in the 1980s.
Introduced for the World Sportscar Championship in 1982, Group C largely avoided a fixed engine-size limit. Instead, cars faced restrictions on fuel capacity, total fuel available and the number of refuelling stops. Teams therefore had to balance outright power against consumption, reliability and pit strategy.
At Le Mans, the first Group C rules allowed a maximum of 2,600 litres for the race, with tanks limited to 100 litres and no more than 25 refuelling operations. The formula made fuel management a central part of performance and helped produce the dominant Porsche 956 and 962 prototypes.
Group B is an easy mix-up because it was introduced alongside Group C, but it primarily covered production-based grand touring cars and became famous in rallying. LMP900 was a much later prototype category, not the 1980s formula that created Le Mans’s fuel-economy contest.