My testing tonight in the preview branch has lead me to believe that insulated tiles are possibly bugged when it comes to accepting heat from liquids. Both magma and hot petroleum apparently are not heating them as much as gases due. It's possible this effects the live branch as well, but I'd have to go back to test it.
As you can see, the tile that's touching the hot hydrogen is heating to some amount, yet the tile just below it touching the magma is not. Even the tile inside the magma is still at it's default 20C temperature. I made sure to save the game and reload it, but the bug still remains. Just below this tank I build a containment tank for steam and this had the expected effect of heating the ceramic tiles some what, but another next to it that I loaded with hot petroleum, the containing ceramic tiles do not heat. The ceramic insulated tiles touching those obsidian tiles are being slightly heated, so it definitely seems like it's just the transfer from liquids that's effected. I have attached the save file in question. I did also test with insulated obsidian tiles and got the same result.
One would expect that dense hot liquids would easily heat these ceramic tiles somewhat, better then gases, for sure.
Steps to Reproduce
Build a tank out of any insulated tiles. Dump hot liquid into it and watch as the insulated tiles don't heat.
This issue has not been confirmed by a developer yet.