just got hands on a very very very nice l-series box for cheap

just wondering about a really high quality oil and where to get it from in perth, i can only find the crappy castrol and stuff brands.
im also willing to pay abit for it too.
any opinions/experiences would be greatly appreciated. Also will it make much difference to the life of the box? Although i will be treating this one like its made of candy glass.
thanks heaps
alex