Oh yes, I forgot about that.
And for more info than you probably wanted....
Many pipeline now don’t even run the spacer (pigs) between the different products.
There is little “mixing” provided the pipeline remains at a velocity that keeps laminar and not turbulent flow inside the pipe.
The little bit of transmix is routed to a slop or transmix tank. That is then tested to see if it can be blended in with diesel or the like and still meet spec, or it is shipped back to a refinery to be separated out again.
Depending on the speed of the analysis equipment and automation with that to valving, the off-spec transmix can be kept to a rather low volume.