Wow, stupid me. I used an underground pipe instead of a straight one, take a look how similar they look compared to each other:

Check this out:



I just don't get it, bug maybe?

Yep, that's exactly why I created this setup in the first place. The circled Refinery however stops working once it produced 11 petroleum. The petroleum coming from that particular refinery won't flow at all, even if connected directly to an empty tank. It works perfectly well for 2 cycles, first ...

Yes the tanks are full but the problem had occured prior to them being filled by the second refinery and still remains once emptying them.

My refinery (the circled one) is stuck @ 11 petroleum, it won't produce neither light oil nor heavy oil anymore. I've been trying to find out why but even with tanks connected directly to the refinery, the petroleum just won't flow. Any ideas?