[0.18.35] Can't connect two same-fluid fluid systems

[eyesathousand]

I attempt to connect two fluid systems: each contains only light oil.
I'm not allowed to do so -- contrary to expectations.
Construction robots are however able to do so.

In the layout, I am converting advanced oil outputs other than petroleum into solid fuel, except for one heavy oil output which is turned into lubricant.

[Loewchen]

I attempt to connect two fluid systems: each contains only light oil.

For this error to occur this can not be true.

[orzelek]

Most likely some part of one of those light oil systems has different fluid or is connected to input/output with different fluid.

It would be nice if game would show you that but currently you need to guess and message displayed is not helpful.

[5thHorseman]

When you click a pipe it gives you a giu with an option to purge fluids from that pipe system. It tells the types of fluids present.

Use that gui to check both pipes for impurities.

The error could be more explanatory, but I've never had it be wrong.

[eyesathousand]

The purge fluids dialogue claims there is lubricant in there, but there is no reason why lubricant ought to be in there.
Mining the pipes and replacing them also leads the box to claim a small amount of lubricant in the system -- despite all the pipes only containing light oil and having never been connected to a lubricant input, output or any indeed any other fluid system whatsoever.
It's a straight line pipe from light oil output to light oil input.

The agreement with the purge fluids dialogue doesn't make the behaviour correct -- merely consistently wrong.

[Loewchen]

Post the save and I find it for you.

[5thHorseman]

The purge fluids dialogue claims there is lubricant in there, but there is no reason why lubricant ought to be in there.

...which is exactly why they explicitly forbade this in the past. Before, when you for no reason would have accidentally mixed a full lube pipe with a full light oil pipe, the game would have stopped you and you'd have seen why. Now, you managed to accidentally get lubricant into your oil pipe but it was long enough ago that you don't remember how or even that it happened.