I’m not so sure that diesel will go up if autos use them. Firstly, I’d bet that automotive diesel is a drop in the bucket compared to heating, trucking usage, and so on. Secondly, as I understand it, you can ship diesel overseas, but gasoline is usually not viable. And, if you want to make a lot of diesel to ship overseas (like from fracking), you have to also make gasoline (this can be tailored to a degree).
What has made diesel very expensive compared to the old days is the “low sulfur” requirement and the additional requirements of the EPA on the fuel and on the autos that use them.
you can ship diesel overseas, but gasoline is usually not viable
Not true. We import gasoline from overseas, and sometimes ship it out that way.
http://www.eia.gov/dnav/pet/pet_move_impcus_a2_nus_epm0f_im0_mbbl_m.htm
http://www.eia.gov/dnav/pet/pet_move_impcus_a2_nus_epobg_im0_mbblpd_m.htm
http://www.eia.gov/dnav/pet/pet_move_expc_a_EPM0F_EEX_mbbl_m.htm
http://www.eia.gov/dnav/pet/pet_move_expc_a_EPOBG_EEX_mbbl_m.htm