Saudi Aramco operates their 400km Ras Tanura to Riyadh product system, (for which I did the hydraulic design) using 2 parallel pipelines, one line runs gasoline only and the other runs two products, Jet A1 and Diesel. Before placing the second line in service, one pipeline ran all products in batch trains ordered by gasoline, diesel, jet, diesel, gasoline. It is definitely possible and common to run a multiproduct operatioin with one pipeline, however in your case only having 6km of length, it is definitely NOT optimum to run batches as too much interface mixture will be created which would require the jet fuel component of that mixture to be sold off as lower value diesel, or the entire interface sent back to a refinery for reprocessing. The more batches you run, the more money lost to interface downgrades. A 6km long pipeline definitely needs to be one product only to be economically viabble.