Redline MT-90 synthetic gear oil
Product Review (submitted on January 30, 2019):
The oil that Red Line recommends, on their website, for our gear boxes is MT-90 75W90 GL-4 gear oil. Our gear boxes were designed for convention (non-synthetic oils) and the clearances are relatively large, larger than for a modern box. A correspondingly heavier oil works well in our boxes, especially for severe applications and boosted cars.