Guy I grew up close to was heavy into Motorbike racing, good racer as well as includes some races in IOM TT in his career. Never won but hell finishing is a win there.
He used to head for small civil airport before a race to stock up on AvGas................. doubt it is same quality as FJ standard but he did rather well in races and never got rumbled.
Doubt it did much damage to the engines but they were always taking them apart between races anyway for cleaning etc