Do a forum search on "600w" and you'll probably get more info than you want.
It should be noted that in the transmission the oils viscosity along with technique are what synchronize the gears for grind free shifting. As the viscosity of the oil goes down the technique must go up and at some point no amount of technique will prevent gear grinding during shifts.
Here's what I use.
http://asm-mexico.com.mx/sitio/admin...0912104421.pdf
It's extremely viscous and unlike STP it's not just an additive but actual gear oil.