#232 SMP engine & tanked oil invisibility

[Jay]

When first logging in, engines that are not animating are invisible.
This is also the case for a few seconds when placing an engine.
They will reappear if you update the state of the block they are located in (redstone current to them will do this, or placing torches/etc)

Oil in a tank is invisible if it is in the tank when you log in, and no oil is being inserted/removed
It can be piped out, and will generally reappear if you loop it back to the same tank, but...