Ok ok... Lock it... Sheesh

Seriously, if you want to race the truck I would not lock it. You don't want wheelies on a track... you want control.

However, if you want to bash mainly, lock the sucker... more fun for sho.

As for what brand of oil, it doesn't really make much of a difference, as long as you use a name brand like Ofna, Mugen or GS.
I'd just get whatever is cheapest, just don't buy some no name off brand oil.