Why do GGR always advise the use of super-unleaded fuel?
As explained above, the valve seats used in the Cosworth engine are compatible with unleaded fuel, and the effectiveness of super-unleaded is greater than four star leaded. (We actually always ran our Group A Sierra Cosworths on super-unleaded fuel). The later (green top) 4×4 Sapphire and Escort Cosworths are designed to use premium unleaded, but we would not recommend this fuel if the performance potential of the car is to be fully exploited.
