Originally Posted by Illsti
Synthetic is too slippery for the synchros, you will most likely grind gears when shifting hard..
So do you want a fluid that causes more friction, heat, and wear, and to boot hurts fuel economy? To make blanket statement saying that synthetic is too slippery for the synchros and is most likely cause someone to grind grears is ill advised. Grinding gears is cause by not having the clutch depressed enough before someone tries to force the gear change (which is also called abuse), or by a fluid that is broken down or has so much contamination in it (because of the forced shifts/gear grinding) to the point where it is not lubricating properly causing even more wear..