So creosote oil has no texture, when viewing in tanks (like the coke oven) it's displayed as black and purple checkers.

In tanks it looks like lava.

Edit: Found the cause of the problem, Artifice provides its own creosote oil which conflicts with RC's oil.

What type of tanks. Railcraft tanks or another mods tanks.

In TE tanks it looks like lava. In BC tanks it has that black and purple checkers look.

I would upload a picture with proof, but my internet is rather sporadic atm. Also, containers of creosote oil are displayed fine.

Edit: I'm almost positive its a conflict with Artifice, as it also adds creosote oil. But there are no options to disable so I can't know for sure.

Double Edit: I took the plunge and completely removed Artifice, it does indeed cause this issue.

Yep, that means the bug resided with Artifice. You'll need to report it to them. Tell them they need to catch the texture atlas event and assign the texture to the fluid.

Example:
https://github.com/CovertJaguar/Railcraft/blob/master/src/main/java/mods/railcraft/common/fluids/RailcraftFluids.java#L147

Also the lack of the ability to disable it is a pretty rude oversight on their part. Its generally considered good form to allow users to decide which implementation to use. There are also cases where the inability to disable a fluid can result in out of sync client/server issues if the client and server don't have identical mod load orders (ie no client only mods).

I'll pass that on, thanks!

@slawr34 I've reported this to them a while ago, I'm sure they fixed it, you might need to update Artifice.