castrol vmx 80 is a good oil for boxes with fibre and three piece synchro cones like the c60, we use it in a lot of gearboxes at work, there is also a better oil that penrite has that is specially designed for the tremac 6 speed gearboxes in the late falcons and commodores, it has polymers in it which soak into the fibre cones and help a lot with the shift, i dont have the name of it on hand, it was a fully synthetic 75, i shall post the name of it on monday when i read it off the bottle! it has proven its weight in gold with all the cars we have put it in so far. but it is also about $55 for 2 litres retail..........