[johnrgrace]

No - higher octane fuels come from the refinery as higher octane - usually because the mix of blending stocks are different and you have to add in some elements to the mix that could have been used to take more lower cost product into "regular" spec.

What happens in pipelines is a lot of the same stuff goes into the pipeline aka "one big slug" at the same time. In between slugs stuff gets mixed and that becomes transmix which gets bought and sold (at a discount) and usually reprocessed and reused. Pipeline scheduling is done to reduce transmix - if high grade gasoline is next to low grade gasoline the transmix could potentially be sold as low grade gasoline.