Actually, I believe product pipelines like the Colonial System ship multiple products in the same line with spacers between.
Moving multiple products from concentrated areas of production to concentrated areas of consumption as a single product is more efficient from both shipping and distribution standpoints.
http://www.colpipe.com/ab_faq.asp
How products are separated in pipelines.
http://www.adventuresinenergy.org/Refined-Product-Pipelines/Batch-Management.html
Multiple fuels like gasoline grades and diesel will ship through the same pipeline. But there are products other than transportation fuels made at a refinery.